incipal 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 regime is that of an
adjuvant food, aiding digestion, favoring increased flow of the
digestive juices, promoting intestinal peristalsis, and not tanning any
portion of t