26o TUBERCULOSIS. 



is SO common in young subjects. In these cases there may- 

 be tubercular ulcera,tion of the intestine, or it may be absent. 

 Woodhead found that out of 127 cases of tuberculosis in children, 

 the mesenteric glands showed tubercular affection in 100, and 

 that there was ulceration of the intestine in 43. It is especially 

 in children that this mode of infection occurs, as in the adult 

 ulceration of the intestine is rare as a primary affection, though 

 it is common in phthisical patients as the result of infection by 

 the baciUi in the sputum which has been swallowed. There is 

 less risk of infection by means of the flesh of tubercular animals, 

 for, as stated by the recent Tuberculosis Commission, in the first 

 place, tuberculosis of the muscles of oxen« being very rare, there 

 is little chance of the bacilli being present in the flesh unless the 

 surface has been smeared with the juice of the tubercular organs, 

 as in the process of cutting up the parts ; and in the second 

 place, even when present they will be destroyed if the meat is 

 thoroughly cooked. 



. We may state, therefore, that the two great modes of infec- 

 tion are by inhalation, and by ingestion, of tubercle bacilli. By 

 the former method the tubercle bacilli will in most cases be 

 derived from the human subject ; in the latter, probably from 

 tubercular cows, though inhaled tubercle bacilli may also be 

 swallowed, and contamination of food by tubercular material 

 from the human subject may occur. Both in inhalation and 

 in ingestion, tubercle bacilli may lodge about the pharynx and 

 thus come to infect the pharyngeal lymphoid tissue, tonsils, etc., 

 tubercular lesions of these parts being much more frequent than 

 was formerly supposed. Thence the cervical lymphatic glands 

 may become infected, and afterwards other groups of glands, 

 bones, or joints, and internal organs. 



Koch's Tuberculin. — In 1890-91 Koch introduced a sub- 

 stance called "tuberculin," as a curative agent for tubercular 

 affections. He stated that if in a guinea-pig suffering from 

 the effects of a subcutaneous inoculation with tubercle baciUi, a 

 second subcutaneous inoculation of tubercle bacilli was practised 

 in another part of the body, superficial ulceration occurred 

 in the primary tubercular nodule, the wound healed, and the 

 animal did not succumb to tuberculosis. This reaction was 

 further studied by means of the above-mentioned tuberculin, 

 which consisted of a concentrated glycerin bouillon culture of 



