3i6 



PATHOGENIC BACTERIA. 



distinctly visible among the granules, giving the tubercle 

 a reticulated appearance. 



As a rule, tubercles steadily increase in size by the in 

 vasion of fresh tissue. The tubercle bacillus does not seem 

 to find the necrotic centres of the tubercles adapted to its 

 growth, and completes its life-cycle with the tissue-cells. 

 It is unusual to find healthy-looking bacilli in the necrotic 



Fig. 69. — Miliary tubercle of the testicle : a, zone of epithelioid cells and 

 leucocytes ; b, area of coagulation-necrosis ; c, giant-cell with its processes : 

 peripherally arranged nuclei and necrotic center ; d, seminiferous tubule (Cam- 

 eron, in International Text- Book of Surgery). 



areas, most of them being observed at the edges of the 

 tubercle, where the nutrition is good. From such edges 

 the bacilli are occasionally picked up by leucocytes and 

 transported through the lymph-spaces, until the phago- 

 cyte falls a prey to its prisoner, dies, and sows the seed 

 of a new tubercle. However, for the spread of tubercle 



