Having gained some information respecting the effects of repeated doses
of caffein on rabbits, it was of interest to find out how carnivora
reacted to the drug when similarly administered. A number of dogs
were used for the purpose. Considerable variation in the mode of
experimentation, as will appear later, was allowed.
Since the condition of the animal, its age, environment, or diet might
be factors influencing toxicity, tests were made on full-grown and
on young growing dogs whose food was varied. The subjects of the
experiment were kept under observation for a few days to several weeks
before the administration of caffein was begun, in order to determine
whether or not any morbid condition existed, as well as to ascertain
whether the new environment had any effect on these animals. Caffein
was given chiefly by mouth, but the subcutaneous method was also
employed during a portion of the experimental period in some dogs. The
initial dose, which varied for different individuals, was maintained
for a variable length of time. It was then progressively increased,
in most cases until the death of the animal. With larger doses the
intervals between successive injections were also increased.