470 
Proceedings of Royed Society of Edinhurgh. [sess. 
Even assuming that venom so introduced is inert, or nearly so, 
as a poison, it does not necessarily follow that it is incapable of 
producing protection ; for this protection is, in part at least, 
dependent on the presence in the blood of a substance or substances 
which possess no distinct toxic action, and which may therefore he 
present in the blood as a result of the administration of venom, 
even although the venom did not produce any evident poisonous 
symptoms. 
In order to obtain some evidence on this subject, the process for 
producing protection already described was applied to a cat, with 
the modification that the doses of venom were introduced into the 
stomach instead of being injected under the skin. 
Taking as a basis the minimum-lethal dose by the latter method of 
administration, the cat received at intervals of from two to five 
days, one-fifth of the minimum-lethal dose on eight occasions, then 
one-fourth, and one-third ; and at longer intervals, the minimum- 
lethal, twice, four times, six times, eight times, ten times, and so 
on, until, on the 116th day, a dose eighty times larger than the 
minimum-lethal was introduced into the stomach. 
hio observable disturbance was produced by any of these doses. 
As in further administrations, doses of upwards of a gramme of 
dry venom would have been required, the experiment was not 
continued beyond this point, for such large quantities would have 
soon exhausted the rapidly-diminishing supply of venom. 
Eight days after the animal had received by the stomach a dose 
of venom representing eighty times the minimum-lethal if given sub- 
cutaneously, a dose of venom corresponding to one and a half times 
the minimum-lethal was injected under the skin. No obvious general 
symptoms followed the administration of this dose, hut some local 
oedema and skin necrosis were produced, and the animal has 
remained in good health until the present time. 
During this experiment, an opportunity occurred for obtaining 
other facts of some interest. It happened that when the adminis- 
trations of venom were commenced, the animal was already 
pregnant, and on the 54th day of the experiment two healthy 
kittens were born. These kittens were fed exclusively on the 
mother’s milk, the mother continuing to receive gradually increasing 
doses of venom. 
