158 JOHNKS DISEASE 



gradually resume their normal healthy state, although 

 in some cases the walls may remain somewhat 

 thickened. In those that die as a result of multiple 

 injections, the lungs are more or less completely 

 solidified, and present a state of static pneumonia. 



The spleen is not much affected except for a certain 

 amount of congestion, although acid-fast bacilli are 

 present from the first day, and persist for at least 

 thirty days. From the beginning practically all are 

 intracellular, but they invariably resist the action of 

 decolorizing agents, and remain well formed or 

 become somewhat granular. The Malpighian bodies 

 are usually quite free from bacilli. 



When present in the spleen, the bacilli are found 

 also in the liver, and may be present from the first 

 to the twentieth or thirtieth day after the last injec- 

 tion. They are phagocytosed by the interstitial cells 

 (Kupffer's cells, sessile macrophages of Metchnikoff), 

 but the true gland cells remain free from bacilli. Some 

 investigators have maintained that the liver gland cells 

 may, under certain circumstances, show phagocytic 

 properties. C. C. Twort and Craig have obtained 

 a remarkably clear picture of the phagocytic power of 

 the interstitial cells, with total inactivity of the gland 

 cells ; the interstitial cells in many cases are crammed 

 with bacilli. The liver soon becomes congested, and 

 from the second to the third day, or even earlier, shows 

 evidence of degeneration; the protoplasm becomes 

 granular, whilst the nuclei remain well formed and 

 stained. The condition is more marked in the hepatic 

 than in the portal zone, as might be expected from 

 the accompanying congestion of the organ. About the 

 third day a lymphatic invasion commences around the 

 portal vessels and bile-ducts ; but in those animals that 

 receive only a single injection it is not extensive, and 



