8 TUBERCULIN AND MALLEIN 



ravages already carried on. Tetanus antitoxin, however, 

 like diphtheria antitoxin, acts as a most powerful prophy- 

 lactic, and it is in this character that its greatest value as a 

 therapeutic agent must be sought. 



Calmette's antivenin has also been found to be of great 

 use in the treatment of snake bite. It is prepared in the 

 same way as are the other antitoxins. By treating a horse 

 with gradually increasing doses of the mixed venom taken 

 from various snakes cobra, black snake, and others it is 

 found that, if sufficient care be taken to give small enough 

 preliminary doses, and to allow the animal to regain weight 

 and condition after each injection, large doses may be given 

 later ; the horse then becomes not only immune against 

 the action of these large doses, but his blood contains an 

 antivenin which, held in solution in the serum, may be in- 

 jected into other animals, where it acts not only as a prophy- 

 lactic, but also as a curative agent against snake bite, even 

 of the most virulent types. 



The products of micro-organisms, however, have been 

 utilised in other most important fashions. Tuberculin 

 (which consists essentially of the products of the tubercle 

 bacillus grown in beef peptone broth containing a five per 

 cent, solution of glycerin, the bacilli destroyed and then 

 filtered out by means of a Pasteur-Chamberland filter, the 

 whole concentrated by evaporation at a low temperature) 

 is now used for the diagnosis of tuberculosis, as it is found 

 that these products, when injected subcutaneously, appear 

 to co-operate with the poisons already in the body, and to 

 cause a reaction of the tissues, and a rise in temperature 

 which, together, give evidence of the presence of a tubercular 

 process. Exactly the same thing happens in the case of 

 mallein, which is prepared in the same way from the 

 glanders bacillus as the tuberculin is prepared from the 

 tubercle bacillus. A small quantity of this substance in- 

 jected subcutaneously in a healthy animal with a normal 

 temperature gives rise to little or no local swelling, and a 

 very slight rise of temperature, whilst a similar quantity 

 injected into a horse suffering from glanders gives rise to 

 a local swelling of considerable size, which goes on increasing 

 up to the thirty-sixth or forty-eighth hour, or even longer, 



