232 TOXINES AND ANTITOXINES. 



CALMETTE 1 has devised the following method for the valuation 

 of snake serum : 



The poison is dried and dissolved in distilled water and the 

 lethal dose for 1 kilo, of rabbit determined. A rabbit weighing 

 2 kilos, is then treated with increasing doses of the serum under 

 examination and the protective dose against a single lethal dose 

 determined. A serum, 1 c.c. of which protects 1 grm. of animal 

 against the single lethal dose, is taken as unity. Thus, if 1 c.c. 

 of the serum under examination protects 2 kilos, of animal, 

 the strength of the serum is two thousand-fold. According to 

 CALMETTE, the minimum strength must be one thousand-fold ; 

 sera of, at least, four thousand-fold strength are used in the 

 tropics. 



This true antitoxic power of the immune serum has nothing 

 to do with the property possessed by ty rosin, cholesterin, &c., 

 of rendering the toxine innocuous, for all these substances act 

 just as they do in the case of tetanus toxine, only combining 

 with the poison in vitro, and never producing immunity. Their 

 action is thus quite distinct from that of the true antitoxines. 



The question whether or no the serum and bile of venomous 

 snakes contain antitoxine stands upon a somewhat different 

 footing. As was found by FRASER, 2 not only is the bile of the 

 cobra particularly active, but also that of the rattlesnake, &c., 

 possesses incomparably greater powers of destroying the poison 

 than the bile of other animals ; and even that of non-venomous 

 snakes has a greater protective power than theirs. This pro- 

 tective function is also retained by alcoholic precipitates of these 

 biles. On the other hand, it must not be lost sight of that, as 

 FRASER 3 himself found, the anti venom is not definitely specific, 

 but that it also acts upon bacterial toxines. 



At the same time, we frequently find that the bile merely has 

 a destructive action upon toxines similar to that of other digestive 

 fluids, so that the question whether or no the bile contains a true 

 antitoxine has not yet been decided. 



Hence, one is hardly justified in attributing the resistance of 

 snakes to this function alone. It is, indeed, more conceivable 

 that the natural immunity of these animals is due to a continual 

 new formation of large quantities of antitoxine, rather than to a 



1 Calmette, " Sur le venin des serpents," Ann. Past., xi., 214, 1897. 



2 Fraser, "The Treatment of Snake Poison with Antivenene," Brit. 

 Med. Journ., ii., 417, 1895; " Antivenomous Properties of the Bile of 

 Serpents," ibid., ii., 125, 1897. 



3 Eraser, "Antitoxic Qualities of the Bile of Serpents," Brit. Med. 

 Journ., ii., 595, 1897. 



