Lesions 671 



tuberculosis of the testicle being more common than of the uterus 

 or ovaries. 



Wounds are also occasional avenues of entrance for tubercle 

 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 familiar 

 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 alimentary 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 whatever 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 bacilli 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 bacilli, 

 instead of being injected en masse into the areolar tissue, are intro- 

 duced by intravenous injection and disseminate themselves singly 

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



