246 VENOMS 
The bleeding is arranged in the following manner: Twelve days 
after the last injection of venom the horse is bled for the first time 
to the extent of 8 litres; five days later it is bled for the second 
time to the extent of 6 litres ; five days later still the third bleeding 
takes place, when 6 litres are again withdrawn. 
The animal is then allowed to rest for three months and sup- 
plied with strengthening food, and during this period 2 grammes 
of venom are again injected on two occasions at the end of a 
month, followed, a month and a half later, by the injection of 
2 more grammes. The antitoxic power of the serum is thus 
maintained approximately at the same standard. 
The serum drawn off at each bleeding must be severely tested, 
which is done by gauging its antitoxic power in vitro, when 
mixed with venom, and also its preventive effect. 
An antivenomous serum may be considered to be utilisable 
when a mixture of 1 c.c. of serum with 0°001 gramme of cobra- 
venom produces no intoxicating effect in the rabbit, and when 
a preventive subcutaneous injection of 2 c.c. of serum into a rabbit 
of about 2 kilogrammes enables it to resist, two hours later, sub- 
cutaneous inoculation with 1 miligramme of venom. 
The preventive power may be very quickly tested by injecting 
a rabbit, in the marginal vein of the right ear for example, with 
2 c.c. of serum, and injecting, five minutes afterwards, in the 
marginal vein of the left ear, 8 milligramme of venom. ‘This 
dose of 1 milligramme generally kills the control rabbits in less 
than thirty minutes when introduced into the veins, and in from 
two to three hours when injected beneath the skin. 
This rapid proof by intravenous injection is extremely striking 
and demonstrative; it can be effected in public during a class or 
lecture in less than an hour, and enables an immediate estimate 
to be formed of the value of an antivenomous serum. When it 
is intended to adopt this method, it is essential to make use of 
a recent solution of venom, for solutions from a week to a fort- 
night old, although sterile, have already lost a large portion of 
