454 Proceedings of Pmjal Society of Edinhurgh. [sess. 
its activity and that of the other venoms being, no doubt, due to 
the above circumstances. 
Experiments were made with cobra-venom on several animals — 
as the guinea-pig, rabbit, white rat, cat, and the innocuous grass 
snake of Italy [Tropedonotus 7iatrix). Very considerable differences 
were found to occur in the minimum-lethal dose for these animals. 
For the guinea-pig, the minimum-lethal dose per kilogramme was 
*00018 grm.; for the rabbit, *000245 grm. ; for the white rat, *00025 
grm. ; for the cat, somewhat less than *005 grm. ; and for the grass 
snake, the relatively large dose of *03 grm.* Cobra venom thus 
takes a position among the most active of known substances, rival- 
ling in its lethal power the most potent of the vegetable active 
principles, such as aconitine, strophanthin, or acokantherin. 
These facts having been ascertained, attempts were next made to 
render animals proof against lethal doses, by administering to them 
a succession of gradually increasing non-lethal doses. These were, 
for the first few doses, in some of the experiments, one-tenth of 
the minimum-lethal, in others one-fifth, in others one-half of the 
minimum-lethal, and in others almost as great as the minimum- 
lethal. At varying intervals, the doses were repeated, and by-and- 
by gradually increased, until the actual minimumdethal had been 
attained. The subsequent doses, by gradual increments, exceeded 
the minimum-lethal, and after five or six times the minimum- 
lethal had been reached, it was found that the increments could be 
further increased, so that each became twice, four times, and latterly 
even five times the minimum-lethal, and still the animal suffered 
little, and, in many cases, no appreciable injury. 
This brief statement, however, does not represent the experi- 
mental difficulties that were encountered. It describes the course 
of events in the altogether successful experiments. Non-success, 
however, was frequent, and many failures occurred before experi- 
ence indicated the precautions and conditions that are necessary for 
success. 
Serpents’ venom exerts what may broadly be described as a 
duplex action. It produces unseen functional disturbances, and it 
* Guinea-pig, nearly ^tli millig. I Kitten (6 weeks), 2 millig. 
Rabbit, nearly ^tli millig. i Cat, 5 millig. 
White Rat, 4th millig. 1 Grass Snake, 3 centig. 
