I076 VENOMS AND ANTIVENINS 



doses are injected intravenously into adult pigeons (300 gm.)- The pigeon which re- 

 sists the highest dose of venom gives the neutralization index of the antivenin. 

 Pigeons are by far the best animals for this type of work because they may react to 

 differences of even o.ooooooi gm, of venom. They are extremely susceptible to 

 venoms as well as most resistant to intercurrent laboratory infections. I have found' 

 that this method can be simplified by keeping the antivenin in contact with the venom 

 during twenty minutes only and at room temperature. The results obtained are com- 

 parable to those of the original method. The main disadvantage of the pigeon test 

 lies, in fact, in that it cannot be used with any degree of accuracy to determine the 

 antitoxic potency of sera upon venoms that possess direct blood-coagulant action 

 when injected intravenously. 



3. Precipitin test. — Calmette and MassoP used a precipitin test as well as the 

 above-mentioned protection test for antivenin titration. They tried to determine the 

 amount of antivenin necessary to make a precipitate appear in a solution of 5 mg. of 

 venom in saline when in contact for one hour at room temperature. The method was 

 afterward modified by various investigators, but has proved to be inaccurate in many 

 cases. Moreover, it is not applicable to all the venoms and antivenins, as I have veri- 

 fied by repeated experiments. 



In my work, it has been found that for an antivenin to be accurately titrated and 

 standardized it is necessary to employ more than one method, the most successful 

 procedure being to associate the neutralization test on pigeons with the determination 

 of both the preventive and the curative potency of the product on white mice and 

 rabbits. 



CONCENTRATION 



The last stage in the preparation of antivenins consists in the purification and 

 concentration of the plasma, which is done in more or less the same way as for 

 diphtheria or tetanus antitoxin, with slight variations. The final pseudo-globulin 

 fraction is filtered, tested for sterility, and then standardized before it is sent out for 

 therapeutic application. 



THERAPEUTIC USE 



Two important factors influence the success of the use of antivenins, viz., early 

 administration and dosage proportional to the amount of poison. In reference to the 

 first factor, it is obvious that the sooner the antivenin is given the better. The sub- 

 cutaneous or intramuscular methods of injection may serve in the majority of cases 

 of snake poisoning, although preference should be given to the intravenous channel 

 whenever the case is of a serious character. When in doubt as to the condition of the 

 patient, it is best not to hesitate but to give the injection 'intravenously. 



The doses of serum should be proportional, not only to the estimated quantity 

 of poison inoculated by the snake, but also to the toxic activity of the poison and to 

 the relative weight of the patient. As in general the larger the snake the greater the 

 quantity of venom it injects, it is advisable to give more than one dose of antivenin 

 in case of a bite by a large reptile. Also, a large dose of antivenin is advised to counter- 



' do Amaral, A.: Snake Venoms, etc., p. 55. Thesis, Harvard School of Public Health, 1924. 

 ^ Calmette, A., and Massol, L.: Ann. de I'Inst. Pasteur, 23, 155. 1909. 



