AFRANIO DO AMARAL 1073 



Gomes,' Houssay and Negrette,* and myself.^ At present we know that for a serum 

 to be really efficacious it must be produced by an animal immunized against the 

 venom of the particular species of snake that has caused the accident or at least that 

 of a closely related species. This means that the principle of the specificity of anti- 

 toxins applies to antivenins. 



Specificity is due to the fact that we may find a similar antigenic composition 

 only among venoms of snakes closely related to each other from a zoological stand- 

 point. Following this principle a number of laboratories have been engaged in the 

 preparation of antivenins against the snakes prevalent in their countries or else- 

 where, but unfortunately, not all of them have closely followed the improvements 

 introduced into the technique of serum therapy during the last ten years. Of the 

 various laboratories or investigators that have in the past prepared or are still prepar- 

 ing on a large scale antivenins for curative purposes, the following are the outstanding: 

 Pasteur Institute (Lille and Paris, France) — against the cobra {N. naja) especially; 

 Institute for Infectious Diseases (Tokio, Japan) — against the habu {T. flavoviridis); 

 Butantan Institute (Sao Paulo, Brazil) — (a) for the rattlesnake (C. terrificiis), (b) for 

 coral snakes (now discontinued), (c) for several of the Brazilian species of Bothrops, 

 (d) for Crotalus and several species of Bothrops (polyvalent), besides others for 

 scorpions and spiders; George Lamb (India) — for the cobra and the daboia; Frank 

 Tidswell (Sydney, Australia) — for the tiger snake; finally, the Bacteriological Insti- 

 tute (Buenos Aires, Argentine) — bivalent serum for C. terrificiis and B. alternata. 



At present the Antivenin Institute of America, Glenolden, Pennsylvania, is pre- 

 paring two sorts of antivenin: (0) "nearctic crotalidic," for the North American 

 rattler, the copperhead, and the moccasin; {b) "bothropic," for the Central American 

 species of Bothrops. 



PREPARATION 



Only four of the various methods which have been developed for the active im- 

 munization of animals seem to have fully succeeded in practice. They are the follow- 

 ing: 



1. Toxoid method.— CohaeXXe in France attempted to destroy the toxophorous 

 group of venom by heat, but was unable to prepare a serum which neutralized even 

 I M.L.D. of the venom used in the immunization. He afterward decided to use as 

 antigens "toxoids" consisting of venom solution plus i :6o calcium hypochlorite solu- 

 tion which destroys the toxic activity of the venom. It is my opinion, however, that 

 the use of these "toxoids" is responsible for the low activity of Calmette's sera. In- 

 deed, the action of chemicals on the venom is likely not only to destroy its toxic 

 principles but to affect its antigenic composition as well. The same criticism is ap- 

 plicable to Phisalix's technique of immunizing animals with only the filterable or the 

 dialyzable fraction, because filtration and dialysis may remove not only toxic but 

 also antigenic principles of the venom. 



2. Mithridatization method. — Brazil, in Sao Paulo, Brazil, always preferred to 

 immunize horses by gradually increasing doses of venom in natura, that is to say, 

 without any previous physical or chemical treatment. The chief advantage of this 



' Gomes, J. F.: Ann. Paulistas med. e dr., 7, i. 1920. 



2 Houssay, B., and Negrette, J.: Rev. Asoc. vied, argent., 36, 223. 1923. 



3 Amaral, A.: Bol. Soc. de med. e cir. S. Paulo, 4, 134. 1921. 



