Rost stated that caffein is eliminated in the urine unchanged after
its introduction into the body and that the amounts found varied with
different species of animals. In the rabbit the amount eliminated was
about 21 per cent; in the dog about 8 per cent; and in the cat somewhat
less than 2.5 per cent. It would appear, therefore, that the cat
decomposes caffein more readily than the rabbit or dog; its resistance
consequently ought to be greater than that of the other animals.
Moderately large doses were accordingly employed in the preliminary
experiments (series A), but the results obtained, as shown in the
protocols, indicated that caffein is fully as toxic for the cat as
for the rabbit or dog. The doses were then decreased and experiments
were performed in order to ascertain the smallest toxic as well as the
smallest fatal dose.