444 THE TUBERCLE BACILLUS GROUP 



Intraperitoneal Inoculation. The disease runs a more rapid course, 

 death usually taking place in from three to eight weeks. The peri- 

 toneum is chiefly involved, particularly when death takes place early. 

 The omentum is thickly studded with tubercles which tend to become 

 confluent and to caseate. Certain mesenteric glands also enlarge and 

 become caseous. As in the subcutaneous inoculation, the inguinal 

 and axillary glands may be involved, but the lesions do not progress 

 so far. 



Ingestion. The lesions usually resemble those of intraperitoneal 

 infection, with, as a rule, more marked lung involvement. 



Inhalation and Pulmonary Inoculation. The lungs contain con- 

 fluent tubercles, many of which are caseated. Not infrequently one 

 or more entire lobes may be involved. Cavity formation, however, 

 is uncommon. The abdominal viscera, particularly the spleen, are 

 involved, as well as the regional lymph glands. 



Products of Clinical Importance Derived from the Tubercle Bacillus. 

 Old Tuberculin (O. T. Koch). Four to six weeks' pure culture of the 

 tubercle bacillus grown in 5 per cent, glycerin broth is killed by heat- 

 ing to 110 C. for half an hour, and then evaporated to one-tenth its 

 original volume on the steam bath. It is then filtered through sterile, 

 unglazed porcelain filters. The resulting fluid, which is dark brown 

 in color, syrupy in consistency, and which keeps in the undiluted con- 

 dition in the cold and away from sunlight for months apparently 

 unchanged, is known as old tuberculin. Old tuberculin contains the 

 water and glycerin-soluble products of metabolism of the tubercle 

 bacillus and products of autolysis of tubercle bacilli which are not 

 precipitated by heat, as well as unchanged concentrated constituents 

 of the broth and about 50 per cent, of glycerin: 0.25 to 0.50 per 

 cent, tricresol is added as a preservative. The nature of the reactive 

 substance or substances in tuberculin is unknown. The composition 

 of tuberculin even when prepared by a uniform technic appears to 

 be variable. 1 Tuberculin prepared from the human type of the tuber- 

 cle bacillus is acid in reaction; that from the bovine type is alkaline. 2 



THE NATURE OF TUBERCULIN. Tuberculin 3 appears to be a true 

 product of the metabolism of the tubercle bacillus. It is thermostabile, 

 dialyzable, insoluble in alcohol, gives no biuret reaction, and is pre- 



1 White and Hollander, The Chemical Composition of Commercial Tuberculins, Trans. 

 9th Ann. Meet. Natl. Assn. Study and Preven. Tuberculosis. 



2 Theobald Smith, Jour. Med. Research, 1905, xiii, 405. 



3 The word "tuberculin" appears to have been used first by Pohl-Pincus, Deutsch. 

 med. Wchnschr., 1884, 108. 



