PRODUCTION OF ANTIVENIN 241 



with this unit. For example, if 0.1 c.c. of normal horse serum was suf- 

 ficient to neutralize the lysin in this experiment, then the antilysin value 

 of the patient's serum is 2. 



According to Arndt and others, a high antilysin content of a serum 

 is to be regarded as indicating a staphylococcic infection, even if it is 

 impossible to establish fixed limits for the values. 



PRODUCTION OF ANTIVENIN 



Snake venom contains two toxins, one being largely neurotoxic and 

 producing paralysis of the respiratory centers, and the other being hemo- 

 toxic and irritant, and producing local necrosis of tissues, hemolysis, 

 etc . In venom poisoning the neurotoxic effect is most dangerous. Largely 

 as the result of the work of Calmette and Fraser an antivenin has been 

 prepared that is capable of counteracting the neurotoxic action not only 

 of cobra venom, but to a lesser extent of other venoms as well. These 

 serums, however, appear to have no effect or but very little upon the 

 irritant toxins. In the poisonous American snakes, such as the rattler, 

 moccasin, and copperhead, the effects of the irritant toxins are largely 

 in evidence, and satisfactory antiserums for these venoms have not 

 been prepared (McFarland). 



In preparing antivenins the toxins, since they are thermolabile, 

 must be used unheated; subcutaneous injections are usually followed by 

 extensive sloughing, and although a certain amount of immunity may 

 be induced in the horse by intravenous injection, there is apparently no 

 protection against the local action of the toxins. 



Preparation of Antivenin. According to Calmette, horses may be 

 immunized by giving them weekly subcutaneous injections of gradually 

 increasing doses of cobra venom, heated to 70 C., for an hour, which 

 precipitates the irritant toxins without injuring the neurotoxin. The 

 initial dose is usually 0.01 gram, gradually increased until, by the end of 

 four months, 4 grams may be given at a single dose. The serum is then 

 tested by mixing increasing doses with the minimal lethal dose for a 

 young rabbit, and injecting the mixtures intravenously into a series of 

 rabbits. 



Since the neurotoxin may prove dangerous in any case of snake-bite, 

 antivenin may be given to advantage, although the local pain and ne- 

 crosis are not relieved by the serum. 



16 



