166 PATHOLOGY OF TYPHUS IN MAN 



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farction due to thrombosis of an artery showed no evidence of 

 bacterial infection. 



The general changes in the spleen may be divided into three 

 types. Early, late, and secondary to extensive confluent 

 bronchopneumonia. The last may be disposed of with the 

 statement that an excess of polymorphonuclear leucocytes is 

 to be found in the blood vessels and reticular tissue of these 

 spleens. The spleens from early cases show marked engorge- 

 ment with blood and considerable phagocytosis of red blood 

 cells by large mononuclear phagocytes. The degree of phago- 

 cytosis, however, is much less than that in typhoid and Rocky 

 Mountain spotted fever. The follicles may or may not exhibit 

 activity as evidenced by size and mitoses. The reticular tissue 

 of the pulp is usually depleted of lymphoid cells, though plasma 

 cells are abundant. 



In late cases the marked engorgement is absent and there 

 is very little phagocytosis. Brown granular pigment, presum- 

 ably hemosiderin, may be abundant. The follicles are usually 

 inactive. Many plasma cells are present at the periphery of 

 follicles and in the pulp. 



In spleens from both early and late cases the follicles may 

 contain (eleven cases) a coarse hyaline fibrin-like reticulum in 

 which polymorphonuclear leucocytes and mononuclear phago- 

 cytes occur. The presence of this material in the follicles bears 

 no relation to the size of the spleen, presence of an important 

 complication or stage of the disease. We regard it as a result 

 of toxic action and its appearance is identical with the deposit 

 in the follicles of spleens in many types of infection. 



Acute lesions of the arteries and veins or the thromboses of 

 typhus were not found in any of the thirty-seven spleens. 



We did not find any evidence of myeloid transformation in 

 the spleen as indicated by Nicol (1919, p. 138) who demon- 

 strated that many cells in typhus spleens give the oxydase 

 reaction. He also states that myelocytes can be seen in sec- 

 tions stained by Giemsa, an observation which we fail to 

 confirm. We did not employ the oxydase reaction in our 

 study. 



