672 



Tuberculosis 



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 

 that the first irritation caused by the bacillus is followed by multi- 

 phcation of the fixed connective-tissue cells of the part. The cells 

 increase in number by karyokinesis, and form a minute cellular 

 collection or primitive tubercle. 



The group of epithelioid cells and lymphocytes constituting 

 the primitive tubercle scarcely reaches visible proportions before 



Fig. 277. — MUiary tubercle of the testicle: a, Zone of epithelioid cells and 

 leukocytes; b, area of coagulation-necrosis; c, giant cell with its processes; per- 

 ipherally arranged nuclei and necrotic center; d, seminiferous tubule (Cameron, 

 in "International Text-book of Surgery"). 



central coagulation-necrosis begins. The cytoplasm of the cells 

 takes on a hyaUne character; the chromatin of the nuclei becomes 

 dissolved in the nuclear juice and gives a pale but homogeneous 

 appearance to the stained nuclei. As the tubercle grows, large 

 protoplasmic masses — giant cells — which contain many nuclei are 

 formed. They sometimes occur near the center, more frequently 

 near the periphery of the lesion. 



Giant cells are not always formed in tubercles, as the necrotic 

 changes are sometimes too rapid and widespread. 



Tubercles are constantly avascular — i.e., in them no new capillary 

 blood-vessels form — and the coagulation-necrosis soon destroys pre- 



