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,
m