PATHOLOGICAL HISTOLOGY 171 



showed lesions common to thrombi remote from their points 

 of origin. 



The renal artery and vein were examined especially in five 

 cases with negative results. 



In one autopsy in which a gross thrombus was noted in the 

 internal saphenous vein the sections show mural thrombi in 

 all respects identical with those found in the skin vessels in 

 typhus. 



The lesions noted above of large blood vessels all seem to 

 take origin in the endothelium and consist essentially of 

 clusters of swollen endothelial cells on or in the intima usually 

 accompanied by clusters of platelets and fibrin. These small 

 mural thrombi are regarded by us as specific typhus lesions, 

 and similar lesions presumably were the points of origin of the 

 gross thrombi noted at post mortem. 



(1) The lymph nodes: The inguinal and mesenteric lymph 

 nodes were studied microscopically from every case. No con- 

 stant changes attributable to typhus were found. The inguinal 

 nodes in most instances contain an excess of mononuclear 

 phagocytic cells (endothelial leucocytes) in their sinuses; in 

 four cases this was very pronounced. Inguinal lymph nodes 

 from two cases (seventh and eleventh day) contain thrombosed 

 arterioles like those found in the skin. 



The mesenteric lymph nodes with few exceptions were nega- 

 tive. In one from a fifteen day case without remarkable 

 features an arteriole in the capsule is thrombosed. In a few 

 instances, accumulations of phagocytic cells in the sinuses 

 comparable to those in the inguinal nodes were found. 



(m) The bone marrow: The marrow from the mid portion of 

 the femur was studied histologically in thirty-two cases. In 

 every case there is some degree of blood forming activity. 

 The degree of activity apparently bears no fixed relation to 

 the duration of the disease but in a general way there is more 

 complete myeloid change in the marrow from late cases. The 

 histological picture in all of these cases is practically that of 

 normal active bone marrow. The marrow in general cannot be 

 distinguished from that of any secondary anaemia and all of 



