A survey of the results obtained in experiments on guinea pigs shows
that the mode of introduction of caffein exerts but little influence
on its toxicity. On careful analysis it will be observed that the
rate of absorption after the administration of caffein by mouth,
subcutaneously, or intraperitoneally is about the same for the
time of appearance of symptoms. The persistence of the symptoms of
caffein intoxication observed in these experiments for 24 hours after
administration points to slow elimination, which may be expected, owing
to the fact that the guinea pigs passed but little urine and caffein
is not diuretic for these animals. The prolonged presence of caffein
in the body probably exerts a harmful influence or after effect, which
may account for the delayed death of some animals many days after a
single dose of caffein was given. Among the factors which undoubtedly
influence toxicity, season should be considered, while the presence
of a diseased condition undoubtedly tends to decrease the resistance
of the guinea pig to caffein. Diet was without any influence on the
toxicity of the single dose of caffein.