CupScout

_General physiological action–Effect on children–Effect on
longevity–Behavior in the alimentary régime–Place in
dietary–Action on bacteria–Use in medicine–Physiological action
of “caffetannic acid”–Of caffeol–Of caffein–Effect of caffein on
mental and motor efficiency–Conclusions_

By Charles W. Trigg

Industrial Fellow of the Mellon Institute of Industrial Research,
Pittsburgh, 1916-1920

The published information regarding the effects of coffee drinking on
the human system is so contradictory in its nature that it is hazardous
to make many generalizations about the physiological behavior of coffee.
Most of the investigations that have been conducted to date have been
characterized by incompleteness and a failure to be sufficiently
comprehensive to eliminate the element of individual idiosyncrasy from
the results obtained. Accordingly, it is possible to select statements
from literature to the effect either that coffee is an “elixir of life,”
or even a poison.

This is a deplorable state of affairs, not calculated to promote the
dissemination of accurate knowledge among the consuming public, but it
may be partly excused upon the grounds that experimental apparatus has
not always been at the level of perfection that it now occupies. Also,
to do justice to some of the able men who have interested themselves in
this problem, it should be said that some of their results were obtained
in researches, distinguished by painstaking accuracy, which have
effected the establishment of the major reactions of ingested coffee.

_The Physiological Action of Coffee_

Drinking of coffee by mankind may be attributed to three causes: the
demand for, and the pleasing effects of, a hot drink (a very small
percentage of the coffee consumed is taken cold), the pleasing reaction
which its flavors excite on the gustatory nerve, and the stimulating
effect which it has upon the body. The flavor is due largely to the
volatile aromatic constituents, “caffeol,” which, when isolated, have a
general depressant action on the system; and the stimulation is caused
by the caffein. The general and specific actions of these individual
components, together with that of the hypothetical “caffetannic acid,”
are considered under separate headings.

Coffee may be considered a member of the general class of adjuvant, or
auxiliary, foods to which other beverages and condiments of negligible
inherent food value belong. Its position on the average menu may be
attributed largely to its palatability and comforting effects. However,
the medicinal value of coffee in the dietary and _per se_ must not be
overlooked.

The ingestion of coffee infusion is always followed by evidences of
stimulation. It acts upon the nervous system as a powerful
cerebro-spinal stimulant, increasing mental activity and quickening the
power of perception, thus making the thoughts more precise and clear,
and intellectual work easier without any evident subsequent depression.
The muscles are caused to contract more vigorously, increasing their
working power without there being any secondary reaction leading to a
diminished capacity for work. Its action upon the circulation is
somewhat antagonistic; for while it tends to increase the rate of the
heart by acting directly on the heart muscle, it tends to decrease it by
stimulating the inhibitory center in the medulla.[188]

The effect on the kidneys is more marked, the diuretic effect being
shown by an increase in water, soluble solids, and of uric acid directly
attributable to the caffein content of the coffee taken. In the
alimentary tract coffee seems to stimulate the oxyntic cells and
slightly to increase the secretion of hydrochloric acid, as well as to
favor intestinal peristalsis. It is difficult to accept reports of
coffee accomplishing both a decrease in metabolism and an increase in
body heat; but if the production of heat by the demethylation of caffein
to form uric acid and a possible repression of perspiration by coffee be
considered, the simultaneous occurrence of these two physiological
reactions may be credited.

The disagreement of medical authorities over the physiological effects
of coffee is quite pronounced. This may be observed by a careful perusal
of the following statements made by these men. It will be noticed that
the majority opinion is that coffee in moderation is not harmful. Just
how much coffee a person may drink, and still remain within the limits
of moderation and temperance, is dependent solely upon the individual
constitution, and should be decided from personal experience rather than
by accepting an arbitrary standard set by some one who professes to be
an authority on the matter.

A writer in the _British Homeopathic Review_[189] says that “the
exciting effects of coffee upon the nervous system exhibit themselves in
all its departments as a temporary exaltation. The emotions are raised
in pitch, the fancies are lively and vivid, benevolence is excited, the
religious sense is stimulated, there is great loquacity…. The
intellectual powers are stimulated, both memory and judgment are
rendered more keen and unusual vivacity of verbal expression rules for a
short time.” He continues:

Hahnemann gives a characteristically careful account of the coffee
headache. If the quantity of coffee taken be immoderately great and
the body be very excitable and quite unused to coffee, there occurs
a semilateral headache from the upper part of the parietal bone to
the base of the brain. The cerebral membranes of this side also
seem to be painfully sensitive, the hands and feet becoming cold,
and sweat appears on the brows and palms. The disposition becomes
irritable and intolerant, anxiety, trembling and restlessness are
apparent…. I have met with headaches of this type which yielded
readily to coffee and with many more in which the indicated remedy
failed to act until the use of coffee as a beverage was abandoned.
The eyes and ears suffer alike from the super-excitation of coffee.
There is a characteristic toothache associated with coffee.

In apparent contradiction of this opinion, Dr. Valentin Nalpasse,[190]
of the Faculty of Medicine of Paris, states:

When coffee is properly made and taken in moderation, it is a most
valuable drink. It facilitates the digestion because it produces a
local excitement. Its principal action gives clear and stable
imaginative power to the brain. By doing that, it makes
intellectual work easy, and, to a certain extent, regulates the
functions of the brain. The thoughts become more precise and clear,
and mental combinations are formed with much greater rapidity.
Under the influence of coffee, the memory is sometimes surprisingly
active, and ideas and words flow with ease and elegance…. Many
people abuse coffee without feeling any bad effect.

Discussing the use and abuse of coffee, I.N. Love[191] says:

The world has in the infusion of coffee one of its most valuable
beverages. It is a prompt diffusible stimulant, antiseptic and
encourager of elimination. In season it supports, tides over
danger, helps the appropriate powers of the system, whips up the
flagging energies, enhances the endurance; but it is in no sense a
food, and for this reason it should be used temperately.

Also Dr. Jonathan Hutchinson[192] makes the following weighty
pronouncement:

In reference to my suggestion to give children tea and coffee. I
may explain that it is done advisedly. There is probably no
objection to their use even at early ages. They arouse the dull,
calm the excitable, prevent headaches, and fit the brain for work.
They preserve the teeth, keep them tight in their place, strengthen
the vocal chords, and prevent sore throat. To stigmatize these
invaluable articles of diet as “nerve stimulants” is an erroneous
expression, for they undoubtedly have a right to rank as nerve
nutrients.

But Dr. Harvey Wiley[193] comes forth with evidence on the other side,
saying:

The effects of the excessive use of coffee, tea, and other natural
caffein beverages is well known. Although the caffein is combined
in these beverages naturally, and they are as a rule taken at meal
times, which mitigates the effects of the caffein, they are
recognized by every one as tending to produce sleeplessness, and
often indigestion, stomach disorders, and a condition which, for
lack of a better term, is described as nervousness…. The
excessive drinking of tea and coffee is acknowledged to be
injurious by practically all specialists.

Dr. V.C. Vaughn,[194] of the University of Michigan, speaking of tea and
coffee, expresses this opinion:

I believe that caffein used as a beverage and in moderation not
only is harmless to the majority of adults, but is beneficial.

This verdict is upheld by the results of a symposium[195] conducted by
the _Medical Times_, in which a large majority of the medical experts
participating, among whom may be enumerated Drs. Lockwood, Wood,
Hollingworth, Robinson, and Barnes, agreed that the drinking of coffee
is not harmful _per se_, but that over-indulgence is the real cause of
any ill effects. This is also true of any ingested material.

Insomnia is a condition frequently attributed to coffee, but that the
authorities disagree on this ground is shown by Wiley’s[196] contention,
“We know beyond doubt that the caffein (in coffee) makes a direct attack
on the nerves and causes insomnia.” While Woods Hutchinson[197]
observes:

Oddly enough, a cup of hot, weak tea or coffee, with plenty of
cream and sugar, will often help you to sleep, for the grateful
warmth and stimulus to the lining of the stomach, drawing the blood
into it and away from the head, will produce more soothing effects
than the small amount of caffein will produce stimulating and
wakeful ones.

The writer has often had people remark to him that while black coffee
sometimes kept them awake, coffee with cream or sugar or both made them
drowsy.

In the course of experiments conducted by Montuori and Pollitzer[198] it
was found that coffee prepared by hot infusion when given by mouth or
hypodermically with the addition of a small dose of alcohol proved an
efficient means of combating the pernicious effects of low temperatures.
Coffee prepared by boiling, and tea, showed negative effects.

The value of coffee as a strength-conserver, and its function of
increasing endurance, morale, and healthfulness, was demonstrated by the
great stress which the military authorities, in the late and in previous
wars, placed upon furnishing the soldiers with plenty of good coffee,
particularly at times when they were under the greatest strain. Various
articles[199] record this fact; and these statements are further borne
out by the data given below in the discussion of the physiological
effects of caffein, to which the majority of the stimulating effects of
coffee may be attributed.

According to Fauvel,[200] with a healthy patient on a vegetable diet,
chocolate and coffee increase the excretion of purins, diminishing the
excretion of uric acid and apparently hindering the precipitation of
uric acid in the organism. This diminution, however, was not due to
retention of uric acid in the organism.

“Habit-forming” is one of the adjectives often used in describing
coffee, but it is a fact that coffee is much less likely than alcoholic
liquors to cause ill effects. A man rarely becomes a slave of coffee;
and excessive drinking of this beverage never produces a state of moral
irresponsibility or leads to the commission of crime. Dr. J.W.
Mallet,[201] in testimony given before a Federal Court, stated that
caffein and coffee were not habit-forming in the correct sense of the
term. His definition of the expression is that the habit formed must be
a detrimental and injurious one–one which becomes so firmly fixed upon
a person forming it that it is thrown off with great difficulty and with
considerable suffering, continuous exercise of the habit increasing the
demand for the habit-forming drug. It is well known that the desire
ceases in a very short period of time after cessation of use of
caffein-containing beverages, so that in that sense, coffee is not
habit-forming.

[Illustration: MEN AND WOMEN LABORERS PICKING COFFEE ON A SÃO PAULO
ESTATE]

[Illustration: SACKING COFFEE IN A WAREHOUSE AT THE PORT OF SANTOS]

[Illustration: PICKING AND SACKING COFFEE IN BRAZIL]

It has been shown by Gourewitsch[202] that the daily administration of
coffee produces a certain degree of tolerance, and that the doses must
be increased to obtain toxic results. Harkness[203] has been quoted as
stating that “taken in moderation; coffee is one of the most wholesome
beverages known. It assists digestion, exhilarates the spirits, and
counteracts the tendency to sleep.” Carl V. Voit,[204] the German
physiological chemist, says this about coffee:

The effect of coffee is that we are bothered less by unpleasant
experiences and become more able to conquer difficulties;
therefore, for the feasting rich, it makes intestinal work after a
meal less evident and drives away the deadly ennui; for the student
it is a means to keep wide awake and fresh; for the worker it makes
the day’s fatigue more bearable.

Dr. Brady[205] believes that the so-called harmfulness of coffee is
mainly psychological, as evidenced by his expression, “Most of the
prejudice which exists against coffee as a beverage is based upon
nothing more than morbid fancy. People of dyspeptic or neurotic
temperament are fond of assuming that coffee must be bad because it is
so good, and accordingly, denying themselves the pleasure of drinking
it.”

The recounting of evidence, both _pro_ and _con_, relevant to the
general effects of coffee could continue almost _ad infinitum_, but the
fairest unification of the various opinions is best quoted from Woods
Hutchinson[206]:

Somewhere from 1 to 3 percent of the community are distinctly
injured or poisoned by tea or coffee, even small amounts producing
burning of the stomach, palpitation of the heart, headache,
eruptions of the skin, sensations of extreme nervousness, and so
on; though the remaining 97 percent are not injured by them in any
appreciable way if consumed in moderation.

So, if one is personally satisfied that he belongs to the abnormal
minority, and has not been argued by fallacious reasoning into his
belief that coffee injures him, he should either reduce his consumption
of coffee or let it alone. Even those most vitally interested in the
commercial side of coffee will admit that this is the logical procedure.

_Effects of Coffee on Children_

The same sort of controversy has raged around the question of the
advisability of giving coffee to children as has occurred regarding its
general action. Dr. J. Hutchinson[207] advocates furnishing children
with coffee, while Dr. Charlotte Abbey[208] is strongly against such a
practise, claiming that use of caffein-containing beverages before the
attainment of full growth will weaken nerve power. Nalpasse[209]
observes that until fully developed the young are immoderately excited
by coffee; and Hawk[210] is of the opinion that to give such a stimulant
to an active school-child is both logically and dietetically incorrect.
Dr. Vaughn[211] advances this scientific argument against the drinking
of coffee by children under seven years of age:

In proportion to body weight the young contain more of the xanthin
bases than adults. They are already laden with these physiological
stimulants, and the additional dose given in tea or coffee may be
harmful.

In a study of the effects of coffee drinking upon 464 school children,
C.K. Taylor[212] found a slight difference in mental ability and
behavior, unfavorable to coffee. About 29 percent of these children
drank no coffee; 46 percent drank a cup a day; 12 percent, 2 cups; 8
percent, 3 cups; and the remainder, 4 or more cups a day. The
measurements of height, weight, and hand strength also showed a slight
advantage in favor of the non-coffee drinkers. If these results be taken
as truly representative, their indication is obvious. However, it seems
desirable to repeat these experiments upon other groups; at the same
time noting carefully the factors of environment, and other diet, before
any criterion is made.

As a refutation to this experimental evidence is the practical
experience of the inhabitants of the Island of Groix, off the Brittany
coast, whose annual consumption of coffee is nearly 30 pounds per
capita, being ingested both as the roasted bean and as an infusion. It
is reported that many of the children are nourished almost entirely on
coffee soup up to ten years of age, yet the mentality and physique of
the populace does not fall below that of others of the same stock and
educational opportunities.[213]

Pertinent in this connection is Hawk’s[214] statement that young mothers
should refrain from the use of coffee, as caffein stimulates the action
of the kidneys and tends to bring about a loss from the body of some of
the salts necessary to the development of the unborn child as well as
for the proper production of milk during the nursing period. The caffein
of coffee also increases the flow of milk, but the milk produced is
correspondingly dilute and a later decreased secretion may be expected.
Furthermore, some of the caffein of the coffee may pass into the
mother’s milk, thus reaching the child, so that the use of coffee during
the nursing period is undesirable on this ground also. Naturally, the
question arises as to whether this arraignment is purely theoretical or
based upon analytical and clinical data.

It is a difficult matter definitely to set an age below which coffee
should not be drunk, as the time of reaching maturity varies with
climate and ancestral origin. Yet, from a theoretical standpoint,
children before or during the adolescent period should be limited to the
use of a rather small amount of tea and coffee as beverages, as their
poise and nerve control have not reached a stage of development
sufficient to warrant the stimulation incident to the consumption of an
appreciable quantity of caffein.

_Coffee Drinking and Longevity_

There are many who would have us believe that the use of coffee is only
a means toward the end of quickly reaching the great beyond; but it is
known that the habitual coffee drinker generally enjoys good health, and
some of the longest-lived people have used it from their earliest youth
without any apparent injury to their health. Nearly every one has an
acquaintance who has lived to a ripe old age despite the use of coffee.
Quoting Metchnikoff[215]:

In some cases centenarians have been much addicted to the drinking
of coffee. The reader will recall Voltaire’s reply when his doctor
described the grave harm that comes from the abuse of coffee, which
acts as a real poison. “Well”, said Voltaire, “I have been
poisoning myself for nearly eighty years.” There are centenarians
who have lived longer than Voltaire and have drunk still more
coffee. Elizabeth Durieux, a native of Savoy, reached the age of
114. Her principal food was coffee, of which she took daily as many
as forty small cups. She was jovial and a boon table companion, and
used black coffee in quantities that would have surprised an Arab.
Her coffee-pot was always on the fire, like the tea-pot in an
English cottage (Lejoncourt, p. 84; Chemin, p. 147).

The entire matter resolves itself into one of individual tolerance,
resistivity, and constitution. Numerous examples of young abstainers who
have died and coffee drinkers who have still lived on can be found, and
_vice versa_, the preponderance of instances being in neither direction.
Bodies of persons killed by accident have been painstakingly examined
for physiological changes attributable to coffee; but no difference
between those of coffee and of non-coffee drinkers (ascertained by
careful investigation of their life history) could be discerned.[216] In
the long run, it is safe to say that the effect of coffee drinking upon
the prolongation or shortening of life is neutral.

_Coffee in the Alimentary Tract_

When coffee is taken _per os_ it passes directly to the stomach, where
its sole immediate action is to dilute the previous contents, just as
other ingested liquids do. Eventually the caffein content is absorbed by
the system, and from thence on a stimulation is apparent. Considerable
conjecture has occurred over the difference in the effects of tea and
coffee, the most feasible explanation advanced being one appearing in
the London _Lancet_.[217]

The caffein tannate of tea is precipitated by weak acids, and the
presumption is that it is precipitated by the gastric juice and,
therefore, the caffein is probably not absorbed until it reaches
the alkaline alimentary tract. In the case of coffee, however, in
whatever form the caffein may be present, it is soluble in both
alkaline and acid fluids, and, therefore, the absorption of the
alkaloid probably takes place in the stomach.

This theory, if true, goes far toward explaining the more rapid
stimulation of coffee.

The statement has sometimes been made that milk or cream causes the
coffee liquid to become coagulated when it comes into contact with the
acids of the stomach. This is true, but does not carry with it the
inference that indigestibility accompanies this coagulation. Milk and
cream, upon reaching the stomach, are coagulated by the gastric juice;
but the casein product formed is not indigestible. These liquids, when
added to coffee, are partially acted upon by the small acid content of
the brew, so that the gastric juice action is not so pronounced, for the
coagulation was started before ingestion, and the coagulable
constituent, casein, is more dilute in the cup as consumed than it is in
milk. Accordingly, the particles formed by it in the stomach will be
relatively smaller and more quickly and easily digested than milk _per
se_. It has been observed that coffee containing milk or cream is not as
stimulating as black coffee. The writer believes that this is probably
due to mechanical inclusion of caffein in the casein and fat particles,
and also to some adsorption of the alkaloid by them. This would
materially retard the absorption of the caffein by the body, spread the
action over a longer period of time, and hence decrease the maximum
stimulation attained.

In a few instances, a small fraction of one percent of coffee users,
there is a certain type of distress, localized chiefly in the alimentary
tract, caused by coffee, which can not be blamed upon the much-maligned
caffein. The irritating elements may be generally classified as
compounds formed upon the addition of cream or milk to the coffee
liquor, volatile constituents, and products formed by hydrolysis of the
fibrous part of the grounds. It may be generally postulated that the
main causation of this discomfort is due to substances formed in the
incorrect brewing of coffee, the effect of which is accentuated by the
addition of cream or milk, when the condition of individual idiosyncrasy
is present.

Without enlarging upon his reason, Lorand[218] concludes that neither
tea nor coffee is advisable for weak stomachs. Nalpasse,[219] however,
believes that coffee taken after meals makes the digestion more perfect
and more rapid, augmenting the secretions, and that it agrees equally
well with people inclined to embonpoint and heavy eaters whose digestion
is slow and difficult. Thompson[220] also observes that coffee drunk in
moderation is a mild stimulant to gastric digestion.

Eder[221] reported, as the result of an inquiry into the action of
coffee on the activity of the stomachs of ruminants, that coffee
infusions produced a transitory increase in the number and intensity of
the movements of the paunch, but that the influence exercised was very
irregular.

An elaborate investigation of the action of tea and coffee on digestion
in the stomach was made by Fraser,[222] in which he found that both
retard peptic digestion, the former to a greater degree than the latter.
The digestion of white of egg, ham, salt beef, and roast beef was much
less affected than that of lamb, fowl, or bread. Coffee seemed actually
to aid the digestion of egg and ham. He attributed the retarding effect
to the tannic acid of the tea and the volatile constituents of the
coffee–the caffein itself favoring digestion rather than otherwise. Tea
increased the production of gas in all but salt foods, whereas coffee
did not. Coffee is, therefore, to be preferred in cases of flatulent
dyspepsia.

Hutchinson, in his _Food and Dietetics_, opines:

As regards the practical inferences to be drawn from experiences
and observations, it may be said that in health the disturbance of
digestion produced by the infused beverages (tea and coffee) is
negligible. Roberts, indeed, goes so far as to suggest that the
slight slowing of digestion which they produce may be favored
rather than otherwise, as tending to compensate for too rapid
digestibility which refinements of manufacture and preparation have
made characteristic of modern foods.

Regarding increase in secretory activity, Moore and Allanston[223]
report that in their experience meat extracts, tea, caffein solution,
and coffee call forth a greater gastric secretion than does water, while
with milk the flow of gastric juice seems to be retarded. Cushing[224]
and others support this statement. This action is partially explained by
Voit on the grounds that all tasty foods increase gastric secretion, the
action being partly psychological; but Cushing observed the same effects
upon introducing coffee directly into the stomachs of animals.

In general, a moderate amount of coffee stimulates appetite, improves
digestion and relieves the sense of plenitude in the stomach. It
increases intestinal peristalsis, acts as a mild laxative, and slightly
stimulates secretion of bile. Excessive use, however, profoundly
disturbs digestive function, and promotes constipation and
hemorrhoids.[225] There is much evidence to support the view that
“neither tea, coffee, nor chicory in dilute solutions has any
deleterious action on the digestive ferments, although in strong
solutions such an action may be manifest.”[226] After conducting
exhaustive experiments with various types of coffee, Lehmann[227]
concluded that ordinary coffee is without effect on the digestion of the
majority of sound persons, and may be used with impunity.

_Coffee in the Dietary–Food Value_

There are three things to be considered in deciding upon the inclusion
of a substance in the dietary–palatability, digestibility without
toxicity or disarrangement, and calorific value. Coffee is as
satisfactory from these viewpoints as any other food product.

The palatability of a well-made cup of good coffee needs no eulogizing;
it speaks for itself. It adds enormously to the attractiveness of the
meal, and to our ability to eat with relish and appetite large amounts
of solid foods, without a subsequent uncomfortable feeling. Wiley[228]
says that the feeling of drowsiness after a full meal is a natural
condition incidental to the proper conduct of digestion, and that to
drive away this natural feeling with coffee must be an interference with
the normal condition. However, if by so doing, we can increase our
over-all efficiency without material harm to our digestive organs (and
we can and do), the procedure has much in its favor both psychologically
and dietetically.

The fact that coffee favors digestion without eventual disarrangement
has been demonstrated above. On the subject of the relative agreement
with the constitution of foods of daily consumption, Dr. English[229]
said:

It is well known that there is no species of diet which invariably
suits all constitutions, nor will that which is palatable and
salutary at one time be equally palatable and salutary at another
time to the same individual. I think the most natural food provided
for us is milk; yet I will engage to show twenty instances where
milk disagrees more than coffee.

Further in this regard, Hutchinson[230] considers that ninety percent of
the “dyspepsias” attributed to coffee are due to malnutrition, or to
food simultaneously ingested, no disease known to the medical profession
being directly attributable to it.

No one cognizant of the facts will contend that a cup of black coffee
has any direct food value; but not so with the roasted bean. This has
quite an appreciable content of protein and fat, both substances of high
calorific value. The inhabitants of the Island of Groix eat the whole
roasted coffee bean in considerable quantity, and seem to obtain
considerable nourishment therefrom. Also, the Galla, a wandering tribe
of Africa, make large use of food balls, about the size of billiard
balls, consisting of pulverized coffee held in shape with fat. One ball
is said to contain a day’s ration; and, because of its food content and
stimulating power, serves to sustain them on long marches of days’
duration.

When an infusion, or decoction, of roasted coffee is made, about 1.25
percent of the extracted matter is protein, it being accompanied by
traces of dextrin and sugar. The same dearth of extraction of food
materials occurs upon infusing coffee substitutes. This small amount can
have but little dietetic significance. However, upon addition of sugar
and of milk or cream, with their content of protein, fat, and lactose,
the calorific value of the cup of coffee rises. Lusk and Gephart[231]
give the food value of an ordinary restaurant cup of coffee as 195.5
calories, and Locke[232] gives it as 156.

Mattei[233] found that 8 cc. of an infusion of roasted Mocha coffee of
five-percent strength suppressed incipient polyneuritis in pigeons
within a few hours’ time. Their weight did not improve, but otherwise
they were completely restored to health. However, in from four to six
weeks after the apparent cure, the symptoms rapidly returned and the
pigeons perished, with symptoms of paralysis and cerebral complications.
The temporary cure was probably due to caffein stimulation and secondary
actions of the volatile constituents of coffee, which may be related to
the vitamines; for it is not likely that the vitamines would withstand
the heat of roasting. If B-vitamine does occur in roasted coffee, it is
present only in traces.[234]

The inclusion of coffee in the average dietary is warranted because of
its evident worth as an aid to digestion and for its assimilating power,
thus earning its characterization as an “adjuvant food.”

_Action of Coffee on Bacteria_

The employment of coffee as an aid to sanitation has been but little
considered. Coffee, when freshly roasted and ground, is deodorant,
antiseptic, and germicidal, probably due to the empyreumatic products
developed during the process of roasting. An infusion of 0.5 percent
inhibits the growth of many pathogenic organisms, and those of 10
percent kill anthrax bacteria in three hours, cholera spirilla in four
hours, and many other bacteria, including those producing typhoid, in
two to six days.[235]

The maintenance of a low rate of contraction of typhoid fever has often
been attributed to drinking of coffee instead of water, the action of
the coffee being partly due to the bactericidal effect of the caffeol
and partly to the boiling of the water before infusion. The stimulating
tendency of the caffein to sustain and to “tide over” those of low
vitalities is also evidenced.

_Use of Coffee in Medicine_

Coffee has been employed in medicinal practise as a direct specific, as
a preventive, and as an antidote. The _United States Dispensatory_[236]
summarizes the uses of caffein and coffee as follows:

Caffein is a valuable remedy in practical medicine as a cerebral
and cardiac stimulant and as a diuretic. In undue _somnolence_, in
_nervous headache_, in _narcotism_, also, at times when the
exigencies of life require excessively prolonged wakefulness,
caffein may be used as the most powerful agent known for producing
wakefulness. In a series of experiments, J. Hughes Bennett found
that within narrow limits there is a direct physiological
antagonism between caffein and morphine. Coffee and caffein in
narcotic poisoning are of value as a means of keeping the patient
awake, and of stimulating the respiratory centres.

As a cardiac stimulant, caffein may be used in any form of heart
failure; the indications for its use are those which call for the
employment of digitalis. It is superior to digitalis in never
disagreeing with the stomach, in having no distinctive cumulative
tendency, and in the promptness of its action. It is pronouncedly
inferior to digitalis in the power and certainty of its action, and
in the permanence of its influence once asserted. As a diuretic it
is superior; it is very valuable in the treatment of _cardiac
dropsies_, and is often useful in _chronic Bright’s disease_ when
there is no irritation of the kidneys.

On account of its tendency to produce wakefulness, it is usually
better to mass the doses early in the day, at least six hours being
left between the last dose and the ordinary time for sleep. From
eight to fifteen grams (of caffein) may be given in the course of a
day in severe cases. If tried, it would probably prove a useful
drug in cases of _sudden collapse_ from various causes.

Good effects of coffee are recounted by Thompson.[237]

It removes the sensation of fatigue in the muscles, and increases
their functional activity; it allays hunger to a limited extent; it
strengthens the heart action; it acts as a diuretic, and increases
the excretion of urea; it has a mildly sudorific influence; it
counteracts nervous exhaustion and stimulates nerve centers. It is
used sometimes as a nervine in cases of migraine, and there are
many persons who can sustain prolonged mental fatigue and strain
from anxiety and worry much better by the use of strong black
coffee. In low delirium, or when the nervous system is overcome by
the use of narcotics or by excessive hemorrhage, strong black
coffee is serviceable to keep the patient from falling into the
drowsiness which soon merges into coma. In such cases as much as
half a pint of strong black coffee may be injected into the rectum.

Strong coffee with a little lemon juice or brandy is often useful
in overcoming a malarial chill or a paroxysm of asthma. It is a
useful temporary cardiac stimulant for children suffering collapse.

Dr. Restrepo,[238] of Medellin, Colombia, claims to have cured many
cases of chronic malaria and related diseases with infusion of green
coffee, after quinine had failed. Wallace[239] states that tincture of
green coffee is a natural and efficacious specific for cholera, and that
she knows of more than a thousand eases of cholera and diarrhea which
have been treated with it without an isolated case of failure.
Landanabileo has been quoted as using raw coffee infusion in hepatic and
nephritic diseases, venal and hepatic colics, and in diabetes.

In the Civil War, surgeons utilized coffee in allaying malarial fever
and other maladies with which they had to contend, often under the most
trying conditions, and with severely limited means of combating
disease.[240] Its effect is to counteract the depressant action of low
and miasmatic atmospheres, opening the secretions which they have
checked. Travelers from the colder climes soon find that the fragrant
cup of coffee is a corrective to derangements of the liver resulting
from climatic conditions.[241]

Dr. Guillasse, of the French Navy, in a paper on typhoid fever, says:

Coffee has given us unhoped for satisfaction, and after having
dispensed it we find, to our great surprise, that its action is as
prompt as it is decisive. No sooner have our patients taken a few
tablespoonfuls of it, than their features become relaxed and they
come to their senses. The next day the improvement is such that we
are tempted to look upon coffee as a specific against typhoid
fever. Under its influence the stupor is dispelled, and the patient
arouses from the state of somnolency in which he has been since
the invasion of the disease. Soon all the functions take their
natural course, and he enters upon convalescence.[242]

Also it has been reported that in extreme cases of yellow fever, coffee
has been used most effectively by many physicians as the main reliance
after all other well known remedies have been administered and failed.

According to Lorand,[243] the use of coffee in gout is strictly
prohibited by Umber and Schittenhelm; but he considered it a mistake
absolutely to forbid coffee, as, when a person has good kidneys, the
small amount of uric acid furnished by the caffein can readily be
eliminated. A curious remedy for gout and rheumatism, the efficacy of
which the writer scouts, is said to be[244]–a pint of hot, strong,
black coffee, which must be perfectly pure, and seasoned with a
teaspoonful of pure black pepper, thoroughly mixed before drinking, and
the preparation taken just before going to bed. If this has any value,
it is probably purely psychological in its function.

Several writers[245] attribute amblyopia and other affections of the
sight to coffee and chicory, without giving much conclusive experimental
data. Beer,[246] a Vienna oculist, however, held that the vapor from
pure, hot, freshly-made coffee is beneficial to the eyes.

Coffee and caffein are physiologically antagonistic to the common
narcotics, nicotine, morphine, opium, alcohol, etc., and are frequently
used as antidotes for these poisons. Binz found that dogs that have been
stupified with alcohol could be awakened with coffee. It may thus be
prescribed for hard drinkers to counteract the baleful excitability
produced by alcohol; in fact, many topers taper off after a long debauch
with coffee containing small amounts of alcoholic beverages. Considering
its ability to counteract the slow intoxication of tobacco, it may be
inferred that coffee is indispensable for hard smokers.

In general, the medicinal value of coffee may be said to be directly
attributable to its caffein content, although its antiseptic properties
are dependent upon the volatile aromatic constituents. Its function is
to raise and to sustain vitalities which have been lowered by disease or
drugs. Although some of the cures attributed to it are probably purely
traditional; still, it must be admitted, that by utilizing its
stimulating qualities in many illnesses the patient may be carried past
the danger point into convalescence.

_Physiological Action of “Caffetannic Acid_”

It has been demonstrated in chapter XVII that there is no definite
compound “caffetannic acid,” and that the heterogeneous material
designated by this name does not possess the properties of tanning.
Further substantiation of this contention, and more evidence of the
innocuous character of the tannin-like compounds in coffee, are
contained in the testimony of Sollmann.[247] “Tannins precipitate
proteins, gelatine, and connective tissue, and thus act as astringents,
styptics, and antiseptics. The different tannins are not equivalent in
these respects. Some (which are perhaps misnamed) such as those of
coffee and ipecac, are practically non-precipitant…. On the whole, one
may say that the small quantities of tannin ordinarily taken with the
food and drink are not injurious, but that large quantities (excessive
tea drinking) are certainly deleterious. The tannin of coffee is
scarcely astringent, and, therefore, lacks this action,” which is proven
by the fact that it does not precipitate proteins.

“It has been claimed that ‘caffetannic acid’ injures the stomach walls,
but there is no evidence that this is so.”[248] Wiley,[249] in reporting
some of his experiments, says: “Apparently the efforts to saddle the
injurious effects of coffee-drinking upon caffetannic acid in any form
in which it may exist in the coffee-extract are not supported by these
recent data.” The fact that tannins retard intestinal peristalsis,
whereas coffee promotes this digestive action, lends further proof to
the non-existence of tannin in coffee. These statements by eminent
authorities may be consolidated into the verity that there is no tannin,
in the true sense of the term, in coffee; and that the constituents of
the coffee brew which have been so designated are physiologically
harmless.

_Physiological Action of Caffeol_

The evidence regarding the physiological action of caffeol is
contradictory in many cases. J. Lehmann found in 1853, that the
“empyreumatic oil of coffee, _caffeone_,” is active; but more recent
investigations have yielded results at variance with this. Hare and
Marshall[250] believe that they proved it to be active. E.T.
Reichert,[251] however, found it inactive in dogs, excepting in so far
that, when given intravenously, it mechanically interfered with the
circulation. With it Binz[252] was able to produce in man only feeble
nervous excitement, with restlessness and increase in the rate and depth
of respirations.

The general effects, as summated by Sollmann[253] are, for _small
doses_, pleasant stimulation; increased respiration; increased heart
rate, but fall of blood pressure; muscular restlessness; insomnia;
perspiration; congestion; for _large doses_, increased peristalsis and
defecation; depression of respiration and heart; fall of blood pressure
and temperature; paralytic phenomena. It is doubtful whether the
quantities taken in the beverage cause any direct central stimulation.

Investigations have also been conducted with the various known
constituents of this “coffee oil.” Erdmann[254] found that in doses of
between 0.5 and 0.6 gram per kilo of body weight, furane-alcohol kills a
rabbit by respiratory paralysis; and that the symptoms of poisoning are
a short primary excitement, salivation, diarrhea, respiratory
depression, continuous fall of the body temperature, and death from
collapse with respiratory failure. In man, doses of from 0.6 to 1 gram
of furane-alcohol increased respiratory activity without producing other
symptoms.

However, man is not as susceptible to these compounds as are the smaller
animals. But even if their relative susceptibility be assumed to be the
same, the lethal dose given the rabbit is equivalent to giving a
140-pound man one dose containing the furane-alcohol content of over
5,000 cups of coffee. Thus, in view of the very apparent minuteness of
the quantity of this compound present in one cup of coffee, together
with the fact that it is not cumulative in its physiological action, the
importance of its toxic properties becomes very inconsequential to even
the most profuse and inveterate coffee drinkers.

Burmann[255] reported the volatile principle to have a reducing action
on the hemoglobin; a depressing effect on the blood pressure; a
depressant action on the central nervous system, disturbing the cardiac
rhythm; and an action on the respiratory centers, causing dyspnea. The
report of Sayre[256] regarding the minimum lethal dose of the
concentrated combined active principles of coffee obtained from dry
distillation is, for frogs, administered intraperitoneally and
subcutaneously, 0.03 cubic centimeters per gram of body weight; for
guinea pigs per stomach, 7.0 cc. per kilogram of body weight, and
administered intravenously and intraperitoneally, about 1.0 cc. per
kilogram.

This evidence regarding the physiological action of caffeol can not in
any wise be construed to indicate a harmfulness of coffee. The
percentage of these volatile substances in a cup of coffee infusion is
so low as to be relatively negligible in its action. And, again, the
caffein content of the brew, as will be seen, tends to counteract any
possible desultory effects of the caffeol.

_General Physiological Action of Caffein_

More attention has been given to the study of the physiological action
of caffein than to that of the other individual constituents of coffee.
Since certain of the effects of coffee drinking have been attributed to
this alkaloid, a brief presentment of the pharmacology of caffein will
be given as an exposition of the many statements made regarding it.
According to the _British Pharmaceutical Codex_[257]:

Caffein exerts three important actions: (1) on the central nervous
system: (2) on muscles, including cardiac: and (3) on the kidney.
The action on the central nervous system is mainly on that part of
the brain connected with psychical functions. It produces a
condition of wakefulness and increased mental activity. The
interpretation of sensory impressions is more perfect and correct,
and thought becomes clearer and quicker. With larger doses of
caffein the action extends from the psychical areas to the motor
area and to the cord, and the patient becomes at first restless and
noisy, and later may show convulsive movements.

Caffein facilitates the performance of all forms of physical work,
and actually increases the total work which can be obtained from
muscle. On the normal man, however, it is impossible to say how
much of the action on the muscle is central and how much
peripheral, but, as fatigue shows itself first by an action on the
center, it is probable that the action of caffein in diminishing
fatigue is mainly central. Caffein accelerates the pulse and
slightly raises blood pressure. It has no action in any way
resembling digitalis; by increasing the irritability of the cardiac
muscle, its prolonged use rather tends to fatigue than to rest the
heart.

Caffein and its allies form a very important group of diuretics.
The urine is generally of a lower specific gravity than normal,
since it contains a lesser proportion of salt and urea; but the
total excretion of solids, both as regards urea, uric acid, and
salts, is increased. Caffein, by exciting the medulla, produces an
initial vaso-constriction of the kidneys, which tends at first to
retard the flow of urine. So in recent years, other drugs have been
introduced, allies of caffein, which act like it on the kidneys,
but are without the stimulant action on the brain. Theobromine is
such a drug.

Another authority states that[258]:

One of the most constant symptoms produced in man by over-doses of
caffein is excessive diuresis, and experiments made upon the lower
animals show that caffein acts as a diuretic not only by
influencing the circulation, but also by directly affecting the
secreting cells, the probabilities being in favor of the first of
these theories of action. According to Schroeder, not only the
water but also the solids of the urine are increased.

The question whether caffein has an influence upon tissue changes
and the consequent nitrogenous elimination can not be considered as
distinctly answered, though the most probable conclusion is that
the action of caffein upon urea elimination and upon general
nutrition is not direct or pronounced. While the therapeutic dose
of caffein is broken up in the body with the formation of
methylxanthin, which escapes with the urine, the toxic dose is at
least in part eliminated by the kidney unchanged.

The metabolism of the methyl purins, of which group caffein is a member,
appears to vary with the quantity ingested. The manner in which the
methyl group is liberated by the cell protoplasm is said[259] to
determine the amount of stimulus which the tissues receive from these
substances. The xanthin group is almost without any excitatory action,
and its metabolic end products are constant. Perhaps the variation in
the excretions of unchanged methylpurins is dependent upon the amount of
total reactive energy they invoke.

Baldi[260] found that caffein in small doses increases muscular
excitability in dogs and frogs. The spinal and muscular hyperic
excitability produced by caffein is, in his opinion, due to the methyl
groups attached to the xanthin nucleus. Fredericq[261] states that
caffein increases the irritability of the cardiac vagus and accelerates
the appearance of pseudofatigue of the vagus which is produced by
prolonged stimulation of the nerve. The action of caffein on the
mammalian heart has also been investigated by Pilcher,[262] who found
that, following the rapid intravenous injection of caffein, there is an
acute fall of blood pressure; and with a maximal quantity of caffein, 10
milligrams per kilogram, the cardiac volume and the amplitude of the
excursions are usually unchanged. With larger quantities, the volume
progressively increases and the amplitude of the excursion decreases.

Salant[263] found that the intravenous injection of 15 to 25 milligrams
of caffein per kilogram in animals was followed by a fall of blood
pressure amounting to 7 to 35 percent in most cases, which was
transitory, although in some animals it remained unchanged. A moderate
rise was rarely observed. Caffein aids the action of nitrates,
acetanilid, ethyl alcohol and amyl alcohol, and increases the toxicity
of barium chloride. In a very thorough study of the toxicity of caffein
which he made with Reiger,[264] a greater toxicity of about 15 to 20
percent by subcutaneous injection than by mouth, and but about one-half
this when injected peritoneally, was found. Intramuscularly the toxicity
is 30 percent greater than subcutaneously. In making the tests on
animals, they found that individuality, season, age, species, and
certain pathological conditions caused variation in the toxic effect of
the administered caffein. Low protein diet tends to decrease resistance
to caffein in dogs, and a milk or meat diet does the same for growing
dogs. Caffein is not cumulative for the rabbit or dog.

As a result of experiments on the action of caffein on the bronchiospasm
caused by peptone (Witte), silk peptone, B-imidoazolyl-ethylamin,
curare, vasodilation, and mucarin, Pal[265] concluded that caffein
stimulates certain branches of the peripheral sympathetic and is thus
enabled to widen the bronchi or remove bronchiospasm.

According to Lapicque[266], caffein produces a change in the
excitability of the medulla of the frog similar to that produced by
raising the temperature of the nerve centers. Schürhoff[267] has
pointed out that the continued use of large quantities of caffein will
produce cardiac irregularity and sleeplessness.

Cochrane[268] cited three cases where caffein was hypodermically
administered in cases of acute indigestion, etc., and concluded that the
cases prove that caffein, or a compound containing it as a synergist,
does indirectly make the injection of morphia a safe proceeding, and
directly increases the force of the heart and arterial tension. However,
Wood[269] found that medium doses of caffein do not produce any marked
rise in blood pressure, and cause a reduction in pulse rate. He
attributes the contradictory results which prior investigations gave, to
employment of unusually large doses and to inaccurate experimental
methods.

Caffein was found by Nonnenbruch and Szyszka[270] to have a slight
action toward accelerating the coagulation time of the blood, being
active over several hours. It inhibits coagulation _in vitrio_. Its
action in the body apparently rests on an increase of the fibrin
ferment. There is no reason to believe that the behavior is dependent on
a toxic action, but there is probably an action on the spleen; for in
several rabbits from which the spleen was removed, no action was
observed.

Experiments conducted by Levinthal[271] gave no positive information as
to the formation of uric acid from caffein in the human organism. The
elimination of caffein has also been studied by Salant and Reiger[272],
who found that larger amounts of caffein are demethylated in carnivora
than in herbivora, and resistance to caffein is inversely as
demethylation, caffein being much more toxic in the former class. In a
similar investigation, Zenetz[273] observed that caffein is very
slightly eliminated from the system by the kidneys, and that its action
on the heart is cumulative; therefore he concludes that it is
contra-indicated in all renal diseases, in arterio-sclerosis, and in
cardiac affections secondary to them. The inaccuracy of these
conclusions regarding the non-elimination of caffein and those of
Albanese,[274] Bondzynski and Gottlieb[275], Leven[276],
Schurtzkwer[277], and Minkowski[278], has been shown by Mendel and
Wardell[279], who point out that many of these experimenters worked with
dogs, in which the chief end-product of purin metabolism is not uric
acid, but allantoin. They observe that the increase in excretion of uric
acid after the addition of caffein to the diet seems to be proportional
to the quantity of caffein taken, and equivalent to from 10 to 15
percent of the ingested caffein. The remainder of the caffein is
probably eliminated as mono-methylpurins.

Regarding the alleged cumulative action of caffein, Pletzer[280],
Liebreich,[281] Szekacs[282], Pawinski,[283] and Seifert[284] all
concluded from their investigations that the action of caffein is
usually of brief duration, and does not have a cumulative effect,
because of its rapid elimination; so that there is no danger of
intoxication.

Dr. Oswald Schmiedeberg says:

Caffein is a means of refreshing bodily and mental activity, so
that this may be prolonged when the condition of fatigue has
already begun to produce restraint, and to call for more severe
exertion of the will, a state which, as is well known, is painful
or disagreeable.

This advantageous effect, in conditions of fatigue, of small
quantities of caffein, as it is commonly taken in coffee or tea,
might, however, by continued use become injurious, if it were in
all cases necessarily exerted; that is to say, if by caffein the
muscles and nerves were directly spurred on to increased activity.
This is not the case, however, and just in this lies the
peculiarity of the effect in question. The muscles and the
simultaneously-acting nerves only under the influence of caffein
respond more easily to the impulse of the will, but do not develop
spontaneous activity; that is, without the co-operation of the
will.

The character of caffein action makes plain that these food
materials do not injure the organism by their caffein content, and
do not by continued use cause any chronic form of illness.

According to Dr. Hollingworth’s[285] deductions, caffein is the only
known stimulant that quickens the functions of the human body without a
subsequent period of depression. His explanation for this behavior is
that “caffein acts as a lubricator for the nervous system, having an
actual physical action whereby the nerves are enabled to do their work
more easily. Other stimulants act on the nerves themselves, causing a
waste of energy, and consequently, according to nature’s law, a period
of depression follows, and the whole process tends to injure the human
machine.” In not a single instance during his experiments at Columbia
University did depression follow the use of caffein.

Of course, caffein, like any other alkaloid, if used to excess will
prove harmful, due to the over-stimulation induced by it. However, taken
in moderate quantities, as in coffee and tea by normal persons, the
conclusions of Hirsch[286] may be taken as correct, namely: caffein is a
mild stimulant, without direct effect on the muscles, the effect
resulting from its own destruction and being temporary and transitory;
it is not a depressant either initially or eventually; and is not
habit-forming but a true stimulant, as distinguished from sedatives and
habit-forming drugs.

_Caffein and Mental and Motor Efficiency_

The literature on the influence of caffein on fatigue has been
summarized, and the older experiments clearly pointed out, by
Rivers[287]. A summary of the most important researches which have had
as their object the determination of the influence of caffein on mental
and motor processes has been made by Hollingworth[288], from whose
monograph much of the following material has been taken.

Increase in the force of muscular contractions was demonstrated in 1892
by De Sarlo and Barnardini[289] for caffein and by Kraepelin for tea.
These investigators used the dynamometer as a measure of the force of
contraction; however, most of the subsequent work on motor processes has
been by the ergographic method. Ugolino Mosso[290], Koch[291].
Rossi[292], Sobieranski[293], Hoch and Kraepelin,[294] Destrée,[295]
Benedicenti,[296] Schumberg,[297] Hellsten,[298] and Joteyko,[299] have
all observed a stimulating effect of caffein on ergographic performance.
Only one investigation of those reported by Rivers failed to find an
appreciable effect, that of Oseretzkowsky and Kraepelin,[300] while
Feré[301] affirms that the effect is only an acceleration of fatigue.

In spite of the general agreement as to the presence of stimulation
there is some dissension regarding whether only the height of the
contractions or their number or both are affected. As might be expected
from the great diversity of methods employed, the quantitative results
also have varied considerably. Carefully controlled experiments by
Rivers and Webber[302] “confirm in general the conclusion reached by all
previous workers that caffein stimulates the capacity for muscular work;
and it is clear that this increase is not due to the various psychical
factors of interest, sensory stimulation, and suggestion, which the
experiments were especially designed to exclude. The greatest increase
… falls, however, far short of that described by some previous
workers, such as Mosso; and it is probable that part of the effect
described by these workers was due to the factors in question.”

Investigations of mental processes under the influence of caffein have
been much less frequent, most notable among which are those of Dietl and
Vintschgau,[303] Dehio,[304] Kraepelin and Hoch,[305] Ach,[306]
Langfeld,[307] and Rivers.[308] Kraepelin[309] observes: “We know that
tea and coffee increase our mental efficiency in a definite way, and we
use these as a means of overcoming mental fatigue … In the morning
these drinks remove the last traces of sleepiness and in the evening
when we still have intellectual tasks to dispose of they aid in keeping
us awake.” Their use induces a greater briskness and clearness of
thought, after which secondary fatigue is either entirely absent or is
very slight.

Tendency toward habituation of the pyschic functions to caffein has been
studied by Wedemeyer[310], who found that in the regular administration
of it in the course of four to five weeks there is a measurable
weakening of its action on psychic processes.

Rivers[311], who seems to have been the first to appreciate fully the
genuine and practical importance of thoroughly controlling the
psychological factors that are likely to play a rôle in such
experiments, concludes that “caffein increases the capacity for both
muscular and mental work, this stimulating action persisting for a
considerable time after the substance has been taken without there being
any evidence, with moderate doses, of reaction leading to diminished
capacity for work, the substance thus really diminishing and not merely
obscuring the effects of fatigue.”

EFFECT OF CAFFEIN ON MENTAL AND MOTOR PROCESSES

Schematic Summary of All Results

St.=Stimulation. 0=No effect. Ret.=Retardation.

PRIMARY EFFECT
Small Doses
| Medium Doses
| | Large Doses
| | | Secondary Reaction
| | | | Action Time Hrs.
| | | | | Duration
| | | | | in Hrs.
Process Tests | | | | | |
Motor speed 1. Tapping St. St. St. None .75-1.5 2-4
Coordination 2. Three-hole St. 0 Ret. None 1-1.5 3-4
3. Typewriting
(a) Speed St. 0 Ret. None Results show
(b) Errors Fewer for all None only in total
doses days’ work
Association 4. Color-naming St. St. St. None 2-2.5 3-4
5. Opposites St. St. St. None 2.5-3 Next
day
6. Calculation St. St. St. None 2.5 Next
day
Choice 7. Discrimination
reaction time Ret. 0 St. None 2-4 Next
day
8. Cancellation Ret. ? St. None 3-5 No
data
9. S-W illusion 0 0 0
General 10. Steadiness ? Unsteadiness None 1-3 3-4
11. Sleep quality Individual differences
12. Sleep quantity depending on body weight 2 ?
13. General health and conditions of
administration

Subsequent to these investigations was that of Hollingworth[312] which
is at once the most comprehensive, carefully conducted, and
scientifically accurate one yet performed. He employed an ample number
of subjects in his experimentation; and both his subjects, and the
assistants who recorded the observations, were in no wise cognizant of
the character or quantity of the dose of caffein administered, the other
experimental conditions being similarly rigorous and extensive.

The purpose of his study was to determine both qualitatively and
quantitatively the effect of caffein on a wide range of mental and motor
processes, by studying the performance of a considerable number of
individuals for a long period of time, under controlled conditions; to
study the way in which this influence is modified by such factors as the
age, sex, weight, idiosyncrasy, and previous caffein habits of the
subjects, and the degree to which it depends on the amount of the dose
and the time and conditions of its administration; and to investigate
the influence of caffein on the general health, quality and amount of
sleep, and food habits of the individual tested.

To obtain this information the chief tests employed were the steadiness,
tapping, coordination, typewriting, color-naming, calculations,
opposites, cancellation, and discrimination tests, the familiar
size-weight illusion, quality and amount of sleep, and general health
and feeling of well-being. A brief review of the results of these tests
is given in the tabular summary.

From these Hollingworth concluded that caffein influenced all the tests
in a given group in much the same way. The effect on motor processes
comes quickly and is transient, while the effect on higher mental
processes comes more slowly and is more persistent. Whether this result
is due to quicker reaction on the part of motor-nerve centers, or
whether it is due to a direct peripheral effect on the muscle tissue is
uncertain, but the indications are that caffein has a direct action on
the muscle tissue, and that this effect is fairly rapid in appearance.
The two principal factors which seem to modify the degree of caffein
influence are _body weight_ and _presence of food_ in the stomach at the
time of ingestion of the caffein. In practically all of the tests the
magnitude of the caffein influence varied inversely with the body
weight, and was most marked when taken on an empty stomach or without
food substance. This variance in action was also true for both the
quality and amount of sleep, and seemed to be accentuated when taken on
successive days; but it did not appear to depend on the age, sex, or
previous caffein habits of the individual. Those who had given up the
use of caffein-containing beverages during the experiment did not report
any craving for the drinks as such, but several expressed a feeling of
annoyance at not having some sort of a warm drink for breakfast.

It is interesting to note that he also found a complete absence of any
trace of secondary depression or of any sort of secondary reaction
consequent upon the stimulation which was so strikingly present in many
of the tests. The production of an increased capacity for work was
clearly demonstrated, the same being a genuine drug effect, and not
merely the effect of excitement, interest, sensory stimulation,
expectation, or suggestion. However, this study does not show whether
this increased capacity comes from a new supply of energy introduced or
rendered available by the drug action, or whether energy already
available comes to be employed more effectively, or whether fatigue
sensations are weakened and the individual’s standard of performance
thereby raised. But they do show that from a standpoint of mental and
productive physical efficiency “the widespread consumption of caffeinic
beverages, even under circumstances in which and by individuals for whom
the use of other drugs is stringently prohibited or decried, is
justified.”

_Conclusion_

Brief summarization of the information available on the pharmacology of
coffee indicates that it should be used in moderation, particularly by
children, the permissible quantity varying with the individual and
ascertainable only through personal observation. Used in moderation, it
will prove a valuable stimulant increasing personal efficiency in mental
and physical labor. Its action in the alimentary régime is that of an
adjuvant food, aiding digestion, favoring increased flow of the
digestive juices, promoting intestinal peristalsis, and not tanning any
portion of the digestive organs. It reacts on the kidneys as a diuretic,
and increases the excretion of uric acid, which, however, is not to be
taken as evidence that it is harmful in gout. Coffee has been indicated
as a specific for various diseases, its functions therein being the
raising and sustaining of low vitalities. Its effect upon longevity is
virtually _nil_. A small proportion of humans who are very nervous may
find coffee undesirable; but sensible consumption of coffee by the
average, normal, non-neurasthenic person will not prove harmful but
beneficial.

[Illustration]