228 TOXINES AND ANTITOXINES. 



acid (up to 3 per cent.), but rapidly destroyed by pepsin-hydro- 

 chloric acid. Exposure to an incubating temperature destroys it 

 to the extent of about 80 per cent. 



4. Neurotoxine, This is fairly resistant to the action of 

 hydrochloric acid (up to 3 per cent.) and to pepsin and papain. 

 It loses about 90 per cent, of its toxicity by being allowed to 

 stand for nineteen days. 



The hsemagglutinine and hsemolysine attack the blood-cor- 

 puscles exclusively, while the hsemorrhagine attacks the endo- 

 thelium of the walls of the vessels, and the neurotoxine the cells 

 of the central nervous system. 



IMMUNISATION AGAINST SNAKE TOXINE. 

 Snake Antitoxine. 



The close relationship between snake toxines and true toxines 

 is shown, above all, by their power of producing an antitoxine. 

 The first attempts to produce immunity against snake venom 

 were those of SEWALL, 1 who used crotalus venom in his 

 experiments. 



CALMETTE succeeded in showing that, even after a single 

 injection of half a lethal dose, the serum of the animal treated 

 had an unmistakable antitoxic action in vitro. ERASER, 2 too, 

 was able to produce antitoxine to the venoms of the cobra, 

 crotalus, diemenia (South Australia), and sepedon (Africa). He 

 obtained preparations capable of resisting as much as fifty times 

 the lethal dose. 



Calmette's method is essentially as follows : About ^ of the 

 lethal dose is first introduced, and this is followed every two or 

 three days by very gradually increasing doses (up to y 1 ^ of the 

 lethal dose). The same result can be obtained with poisons 

 chemically weakened by means of gold chloride or calcium 

 chloride (CALMETTE 3 ). 



After four or five weeks the animals can resist twice the lethal 

 dose. They can then be treated every eight or ten days with 

 larger doses, until a very high degree of immunity can be pro- 



1 Sewall, " Exper. on the Preventive Inoculation of Rattlesnake Venom," 

 Journ. of PhysioL, viii., 203, 1887. 



2 Fraser, "Immunity against Snake Poison," Brit. Med. Journ., i., 1309, 

 1895. 



3 Calmette, " Proprie'te's du serum des animaux immunises centre le 

 venin des serpents," Comptes Rend., cxviii., 120, 1004, 1894. 



