602 INFECTION AND IMMUNITY. 



parently indifferent substances as trypsin, peptone 

 (albumose), sodium cinnamate and the "mycopro- 

 teins" of other bacteria provides additional sup- 

 port to this view. On the other hand, since rela- 

 tively large amounts of these indifferent sub- 

 stances are required to produce the reaction, where- 

 as minute amounts of tuberculin suffice, others 

 hold that the specificity of the latter substance 

 may be maintained. 



Early tuberculosis reacts to tuberculin in the 

 most typical manner. On account of the fact that 

 latent or healing cases may respond to the test, its 

 positive outcome gives no indication of the serious- 

 ness of the patient's condition, which is a practical 

 question of some importance. 



(?) The fear that tuberculin, in producing an in- 

 flammatory reaction around tuberculous areas, 

 may cause a dissemination of the bacilli, has acted 

 strongly in preventing the use of the toxin for 

 both diagnostic and therapeutic purposes. On a 

 priori grounds, such an event would seem to be a 

 possibility, for, with the inflammation, the vessels 

 surrounding the tubercles become congested, new 

 leucocytes accumulate and there is an extravasation 

 of fluid. Since during the subsidence of the in- 

 flammation a certain number of leucocytes may 

 again leave the area and as the extravasated fluid 

 returns to the circulation, bacilli may be carried to 

 other tissues by them. Contrary to such reasoning, 

 however, the observations of Koch and his follow- 

 ers in animal experiments and in the diagnostic 

 and therapeutic use of tuberculin in man, lead 

 them to say that tuberculin when properly ad- 

 ministered never causes an aggravation or exten- 

 sion of the disease. Similar conclusions were 



