EI-FKCTS OF SNAKl'; \'KNOMS ON DOMKSTIC ANIMALS. 349 



of antivenonions serum a'sjainst the comtruMier varieties — namely, 

 Bitis aricfaiis. Naja uigricoUis aiul Pla^'a and Sepcdon hcciua- 

 tochilus. 



Unfortunately tlic records of these earhcr experiments are 

 not available, but antivenomous serum of an activity equal to 

 Calmette's for use ag'ainst jiuff-adder and cobra was issued from 

 the Pietermaritzburi^ Laboratory about i^o^. Watkins-I'itchford 

 employed horses and mules, and in the earlier stages the tech- 

 nique was based on that of Calmette. namely, subcutaneous injec- 

 tions of venom at definite intervals. It was found, however, 

 that the (juantity of ven<)m re((uired successfullv to immunise 

 a horse was so great that there was much difhculty in obtaining 

 sufificient sui)plies. and, further, that this meth(xl. owing to the 

 variable production of an extensive local lesion at the site of 

 injection, could not be successfully carried out with puff-adder 

 venom. It was. therefore, decided to endeavour to hyperimmu- 

 nise the animals by intravenous injections of venom. This was 

 done, and the results were so satisfactory that the method was 

 adopted, and is still being utilised for tlie jiroduction of anti- 

 venomous serum. The advantages over the method of Cahuette 

 are: (i) 1liat a very much smaller quantity of venom is ref[uired 

 to produce serum having the necessary acti\'ity. (2) That it is 

 now possible to produce an anti-viperine serum without delay due 

 to abscess formation and other complications affecting the site of 

 injection. (3) There is practically no loss of condition in the 

 animals mider treatment, such as was reported by Calmette. (4) 

 The antivenomous activity of the serum is found on test to 

 compare very favoura]:)ly with that produced by Calmette. 



The method, however, has two disadvantages — (i) the ten- 

 dency to thrombosis of the vein into which the venom was 

 injected; (2) the very acute reaction which follows almost imme- 

 diately after the venom is injected, due to the very rapid distri- 

 bution of the venom through the system. The details of this 

 method are as follows : — 



The animal selected should be young, but full grown and in 

 good condition. Horses of a dull, lethargic temperament do not 

 appear to stand the injections as well as those of a more spirited 

 nature. The neck should not be fleshy, as in such cases if the 

 venom accidentally gets into the subcutaneous tissue surround- 

 ing the vein a swelling results, and the vein becomes difficult 

 to punctm-e. 



The dose of prescribed venom to be injected is carefully 

 weighed and dissolved with from 5 c.c. to 10 c.c. of distilled 

 water, and sucked into a suitable syringe. A needle free from 

 venom is then introduced into the jugular vein, which has been 

 raised by digital pressure, the syringe is connected to the needle, 

 and the piston is then raised until blood is drawn into the syringe. 

 The pressure on the vein is released, and the contents of the 

 syringe slowdy injected. It is a good plan to have the jugular 

 vein compressed so that a little blood is again sucked up into the 

 syringe, which, when injected, ensures that all the venom solution 



