714 Tuberculosis 



bacilli. Anatomic tubercles are not uncommon upon the hands of 

 anatomists and pathologists, most of these growths being tuberculous 

 in nature. Such dermal lesions usually contain few bacilli. 



Lesions. — The macroscopic lesions of tuberculosis are too famihar 

 to require a description of any considerable length. They consist 

 of nodules, or collections of nodules, • called tubercles, irregularly 

 scattered through the tissues, which are more or less disorganized 

 by their presence and retrogressive changes. 



When tubercle bacilli are introduced beneath the skin of a guinea- 

 pig, the animal shows no sign of disease for a week or two, then begins 

 to lose appetite, and gradually diminishes in flesh and weight. Ex- 

 amination usually shows a nodule at the point of inoculation and 

 enlargement of the neighboring lymphatic glands. The atrophy 

 increases, the animal shows a febrile reaction, and dies at the end of 

 a period of time varying from three to six weeks. Post-mortem ex- 

 amination usually shows a cluster of tubercles at the point of inocu- 

 lation, tuberculous enlargement of lymphatic glands both near and 

 remote from the primary lesion, and a widespread tuberculous in- 

 vasion of the lungs, liver, spleen, peritoneum, and other organs. 

 Tubercle bacilli are demonstrable in immense numbers in all the 

 invaded tissues. The disease in the guinea-pig is usually more 

 widespread than in other animals because of its greater susceptibility, 

 and the death of the animal occurs more rapidly for the same reason. 

 Intraperitoneal injection of tubercle bacilli in guinea-pigs causes a 

 still more rapid disease, accompanied by widespread lesions of the 

 abdominal organs. The animals die in from three to four weeks. 

 In rabbits the disease runs a longer course with similar lesions. In 

 cattle and sheep the infection is commonly first seen in the alimen- 

 tary apparatus and associated organs, and may be limited to them 

 though primary pulmonary disease also occurs. In man the disease 

 is chiefly pulmonary, though gastro-intestinal and general miliary 

 tuberculosis are common. The development of the lesions in what- 

 ever tissue or animal always depends upon the distribution of the 

 bacilli by the lymph or the blood. 



The experiments of Koch, Prudden, and Hodenpyl,* and others 

 have shown that when dead tubercle baciUi are injected into the 

 subcutaneous tissues of rabbits, small local abscesses develop in the 

 course of a couple of weeks, showing that the tubercle bacilli possess 

 chemotactic. properties. These chemotactic properties seem to 

 depend upon some other irritant than that by which the chief lesions 

 of tuberculosis are caused. When the dead tubercle baciUi, instead 

 of being injected en masse into the areolar tissue, are introduced by 

 intravenous injection and disseminate themselves singly or in small 

 groups, the result is quite different and the lesions closely resemble 

 those caused by the living organisms. 



Baumgarten, whose researches were made upon the iris, found 

 * "New York Med. Jour.," June 6-20, 1891. 



