236 Manual of Veterinary Microbiology. 



a guinea pig wliich lias been inoculated eiglit to ten 

 weeks before ; it requires twenty to thirty centigrams, 

 sometimes even as much as fifty centigrams, to kill a 

 guinea pig inoculated four to five weeks before. The 

 guinea pigs die in six to thirty hours, according to 

 the extent of the tubercular process. 



Tuberculin, after twenty-four hours' treatment with 

 two to three volumes of alcohol, yields up its active 

 substance in the form of a precipitate of an albuminoid 

 nature. 



Tuberculin causes in tuberculous subjects : 



1st. A more or less intense febrile reaction which 

 supervenes after several hours, usually from the tenth 

 to the twentieth ; 



2d. A quite remarkable inflammatory reaction 

 around the tuberculous foci. This substance is there- 

 fore pyretogenic and phlogogenic, but as the first of 

 these actions produces its effects indirectly it is some- 

 what delayed. According to Gamaleia, the mode of 

 action of tuberculin is somewhat as follows : It pos- 

 sesses properties which are especially toxic for the ele- 

 ments of the tubercle, cause them to undergo necro- 

 biosis in the same way as the secretions of the bacillus 

 contained in the lesions produce necrobiosis (under 

 the form of caseation or softening) of the central parts 

 of the latter. Now, the proteins resulting from the 

 decomposition of the elements thus attacked excite a 

 local exudative inflammation and leucocytic infiltra- 

 tion. This local reaction results in the breaking up 

 and elimination of the tubercular foci. The febrile 

 reaction must be attributed to the absorption of the 

 necrosed tissues. (See page 64, Gangolphe and 

 Courmont.) 



