1894-5.] Antivenene and Serpents Blood-Serum. 
465 
Further Observations on Antivenene, and on the Pro- 
duction of Immunity against Serpents’ Venom ; with 
an Account of the Antidotal Properties of the Blood- 
Serum of Venomous Serpents. By Professor Fraser, 
M.D., F.E.S. 
(Read July 15, 1895.) 
{Ahstract.) 
At the time when my former paper was communicated to the 
Society, I was engaged in investigating several subjects closely 
related to those dealt with in that paper, but in regard to which 
the experimental work had not advanced sufficiently to allow 
definite statements to be made. 
I propose, to-night, to make some statements on these subjects. 
Antivenene of Rahhits protected against fifty times tlie minimum- 
lethal dose. — A description has already been given of the steps by 
which protection against fifty times the minimum-lethal dose of cobra 
venom had been produced in rabbits. The antidotal power of the 
antivenene derived from these rabbits has now been examined. 
When this antivenene was mixed with twice the minimum-lethal dose 
of cobra venom and the mixture injected under the skin of a rabbit, it 
was found that recovery occurred if the dose of antivenene was '7 c.c. 
or *6 C.C., but that the animal died if the dose was *5 c.c. or A c.c. per 
kilogramme. As *65 c.c. per kilogramme of the antivenene derived 
from rabbits which had last received thirty times the minimum-lethal 
dose is able to prevent death when mixed with the same lethal dose 
of venom, this result is an unexpected one. It appears to show that 
the blood-serum of a rabbit which had last received thirty times the 
minimum-lethal dose of venom is almost as powerful as an antidote 
as the blood-serum of a rabbit which had last received fifty times the 
minimum-lethal dose. If this be the case, it is suggested that for any 
given species of animal there is a maximum limit to the quantity of 
antivenene which can be produced or retained in the blood, and that, 
in the case of the rabbit, this maximum limit is reached when the dose 
is thirty times the minimum-lethal or even somewhat less. It is also 
suggested that this maximum- limit is reached before the maximum 
protection of the animal has been produced ; for, undoubtedly, an 
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