ANTI- VENOMOUS SERUM AND ITS PREPARATION. 421 



a single injection without showing any signs of poisoning. When 

 this high degree of tolerance has been reached, which takes about 

 one and a half years to accomplish, the animal is considered to 

 be sufficiently immune for the preparation of anti-venomous 

 serum for the treatment of snake venom poisoning. The follow- 

 ing is the process of extraction of blood and preparation of the 

 anti-venomous serum employed at the Lille Institute, and ex- 

 plained by Dr. Calmette in his classical work on " 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 eight litres (roughly seven quarts) ; 

 five days later it is bled for the second time to the extent of six 

 litres (about five quarts) ; five days later still the third bleeding 

 takes place when six litres are again withdrawn. 



"The animal is then allowed to rest for six months and supphed 

 with strengthening food, and during this period two 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 

 two more grammes. The anti-toxic 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 anti-toxic power in vitro 

 when mixed with venom, and also its preventive effect. 



" An anti-venomous serum maybe considered to be utilizable 

 when a mixture of i c.c. of serum with o'ooi 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 two kilogrammes enables it to resist, two hours 

 later, subcutaneous inoculation with one milhgramme of venom. 

 The preventive power may be 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, eight milligrammes of venom. A 

 dose of one 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." 



There is no rapid way of rendering animals or man immune 

 to snake venom. In all snake-infested countries the natives 

 and colonists have implicit faith in various substances, mostly 

 of a vegetable nature, all the best known of which in South 



