THE RENDERING OF ANIMALS IMMUNE, 117 



Aktificial Immunity. 



Notwithstanding these diffisulties however, such gratifying results have 

 been obtained as that rabbits could at last receive by subcutaneous injection 

 so much as ten, twenty, thirty, and even the remarkable quantity of fifty 

 times the minimum lethal dose without manifesting any obvious symptoms of 

 poisoning. 



Almost the only observable phenomena were a rise in the body tempera- 

 ture, which continued for a few hours after the injection, and which contrasts 

 with the fall that occurs after the administration of even non-lethal doses in 

 non-protected animals, and a loss of appetite which usually, though not inva- 

 riably, occurred, and was probably the cause of a temporary fall in weight 

 during the day or two days succeeding each injection. On the other hand 

 during the process of successful immunisation the animals increased in weight, 

 they fed well, and appeared to acquire increased vigour and liveliness. This 

 has been frequently exemplified in the smaller animals, such as rabbits ; and 

 also, very conspicuously, in an aged and previously sedate horse, which in the 

 process of immunisation has now received ten times the estimated minimum 

 lethal dose. 



It is marvellous to observe these evidences of the absence of injurious 

 effects and even of the production of benefit in an animal which, for instance, 

 has received in one single dose a quantity of venom sufiicient to kill, in less 

 than two hours, fifty animals of the same weight, and in the course of five or 

 six months a total quantity of venom sufficient to destroy the lives of 370 

 animals of the same species and weight. 



With the cobra venom I have also immunised catsj both by subcutaneous 

 and by stomach administration ; but the significance of the latter method of 

 administration must be reserved for a future communication. As I have 

 stated, a horse is also being immunised ; and I have to express my obligations 

 to Principal Williams for granting me the accommodation of his establishment, 

 and to Professor Davis, also of the New Veterinary College, for much valu- 

 able assistance. 



Following the same plan of research with the three other venoms, it was 

 found that the minimum lethal dose per kilogramme for rabbits of the dia- 

 mantina venom is 0*0015 g, ; of the venom of Sepedon hcemachates 0'0025 g. ; and 

 of the venom of Crotalus 0'004 g,^ The Crotalus venom is, in its purity, alto- 

 gether comparable with the cobra venom ; and the determinations, therefore 

 show that cobra venom is sixteen times more powerful than crotalus or 

 rattlesnake venom. This venom, as well as the two others, however much 

 exceed cobra venom in the intensity of their local action. When death is 

 produced by crotalus venom, the subcutaneous tissues became extensively 

 infiltrated with a large quantity of blood and of blood-stained serum the 



Diamantina venom, 1| mg, ; Sepedon hcemachates, 2i mg.; Crotalus horridus, i m". 



