VACCINATION AGAINST SNAKE-VENOM 247 
their toxicity, and, if these be employed, the dose of venom 
calculated to kill the control animals in thirty minutes, for 
example, takes an hour or more to do so. 
I always prepare my test solutions of venom in the following 
manner :— 
Ten milligrammes of dry cobra-venom are weighed in a delicate 
balance. The venom is dissolved in 10 c.c. of 0°8 per cent. physio- 
logical salt solution, which takes a few minutes. When the venom 
is thoroughly dissolved it is transferred to a test-tube, which is 
immersed for three-quarters of an hour in a water-bath heated to 
+ 72° C. In this way the non-toxic albumins are coagulated 
without modifying the neurotoxic substance. The solution is 
poured on to a filter of sterilised paper, and the clear liquid 
which is collected is immediately put up in glass phials, which 
are hermetically sealed, or in small sterilised bottles. Its toxicity 
is tested upon control animals, and it may be kept for five or 
six days if protected from light, or for several weeks in a refrigerator 
at about 0° C. 
One-tenth of this solution corresponds exactly to 1 milligramme 
of dry venom. 
As for the antivenomous serum, as soon as its antitoxic value 
has been ascertained by the methods that I have just described, and 
it has been separated from clots and red corpuscles by suitable 
decantation, it is portioned out, with the usual aseptic pre- 
cautions, into small sterilised bottles of 10 c.c. capacity, without 
the addition of any antiseptic. 
In order to ensure that it will keep for a long time, care is 
then taken to heat the hermetically sealed bottles in a water-bath 
at a temperature of 58° C. for one hour, and this operation is 
repeated for three days in succession. 
Serum prepared in this way preserves its antitoxic power 
unimpaired for about two years, in all climates. I have had 
occasion at various times to receive bottles which had been sent 
eighteen months and two years previously to India and Indo-China, 
