BACTERIUM TUBERCULOSIS 135 



leaving any inflammation at their point of entry. After 

 having entered the tissues proper they may be carried any- 

 where by the lymph and probably by the blood. 



Tubercles. Having settled at a point of low resistance, 

 they irritate tha tissue rather slowly to produce a localized 

 inflammation which is called a tubercle, a gray body about 

 the size of a millet seed. The cells composing this little mass 

 are very much the same as those seen in chronic local non- 

 tuberculous inflammations, but their arrangement, partic- 

 ularly when combined with large cells having numerous 

 nuclei about their edge (giant cells), is rather characteristic 

 of the disease. Many of these tubercles spread centrifugally 

 and coalesce. The center of the tubercles, being devoid of 

 nutriment, since the blood supply is cut off, undergoes cheese- 

 like or caseous softening. The combination of many tubercles 

 and their destroyed center produces large caseous abscesses. 

 When these are in the lungs the softened centers may be 

 removed by being coughed up after the process has ulcerated 

 into an air passage. In the kidney the same general thing 

 may occur, and the softened matter goes into the urine. 



Forms of Tuberculosis. When the process ulcerates into 

 the blood supply there may result a rapid dissemination of the 

 bacteria throughout the body, with the production of innu- 

 merable miliary tubercles everywhere. Among the special 

 forms of tuberculosis are meningitis, hip disease, and spine 

 (Pott's) disease. The first is a long-standing inflammation in 

 which the coverings of the brain and cord and the superficial 

 layers of these organs are involved in an extensive inflamma- 

 tion. The hip and spine diseases arise when the bacteria get 

 into the soft marrow of the bones, and extend to the joint 

 and tissues about it. 



Toxins. The peculiar evidences of tuberculosis are due to 

 the toxins elaborated by the causative germ, which are both 

 extracellular and endotoxic. The former produce the con- 

 stitutional symptoms of fever and general depression of 

 health. They are also probably responsible for some of the 



