THE MICROBIAL TOXINS. 71 



tion with an elevation of temperature of 1.5 to 

 3 C., whereas if the animal is not tuberculous 

 no such reaction takes place. 



Cases in which tuberculosis is far advanced, and 

 in which the organism is impregnated with tuber- 

 culin, do not react after the injection of tuberculin.* 



Tuberculin does not confer immunity, and the 

 bacillus retains all its virulence, even in injected 

 tissues; nevertheless, the return to health of ani- 

 mals in which injections have been recently made 

 may be due to the action of large doses of the 

 serum; and on the other hand the tuberculin, in 

 large quantities, may render the location unsuit- 

 able for the development of the tubercle bacilli. 



Diphtheria Toxin. The most characteristic prop- 

 erty of the diphtheria bacillus is the production, in 

 culture media, of a special toxic substance which 

 has been named diphtheritic toxin; this name, 

 however, has come to be also extended to a liquid 

 in which the bacilli have lived, and which has 

 been sterilized by nitration or by any other suita- 

 ble process. 



Roux and Yersin f were the first to affirm that 

 diphtheria is an autointoxication caused by a very 

 active poison formed by the microbe in the restricted 

 locality where it develops. In order to obtain this 



* NOCARD and LECLAINCHE: Les Maladies Microbiennes 

 des Animaux. 



f Annal. de VInstit. Pasteur, n, p. 632, and vni, p. 611. 



