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 tlie extent of htres ; 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 takes place, when 6 litres are again withdrawn.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 oif 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 seram may be considered to be utilisable 

 when a mixture of 1 c.c. of serum with "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 milligramme of venom. 



The preventive power may be very quickly tested by injecting 

 a rabbit, in the marginal vein of tlie right ear for example, with 

 2 c.c. of serum, and injecting, five minutes afterivards, 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 



