PATHOLOGICAL HISTOLOGY 165 



Focal infiltrations are found occasionally in the endocardium 

 and in one case (Autopsy No. 18), in which there was throm- 

 bosis of the internal carotid artery, microscopic mural thrombi 

 were attached to the endocardium in recesses between columnae 

 carnae. (Plate XXV, fig. 59.) 



In striking contrast to the skin, large blood vessels in the 

 heart and pericardium very rarely contain lesions. A rare 

 arteriole and venule contain mural thrombi in the whole of 

 our series. The vascular lesions are almost wholly restricted 

 to capillaries and vessels of pre-capillary size lying in the 

 substance of the myocardium, and the vessels in the con- 

 nective tissue septa have with rare exceptions escaped lesions. 

 Small hemorrhages surrounding capillaries packed with en- 

 dothelial cells and polymorphonuclear leucocytes is a rare 

 finding. 



The most extensive lesions were invariably present in the 

 papillary muscle and adjacent ventricle wall. We have not 

 succeeded in demonstrating rickettsia satisfactorily in the 

 heart lesions. No groups like those found in the skin lesions 

 were found. The endothelial cells concerned in the heart 

 lesions contain so many inclusions that the occasional presence 

 of one or several pairs of rickettsia-like bodies cannot be ac- 

 cepted with assurance. 



(c) The lungs: Slides for microscopic examination were 

 taken from portions of the lung most nearly normal as well as 

 from portions with lesions. No lesions peculiar to typhus were 

 found. In one instance only was there thrombosis of blood 

 vessels. The bronchitis and bronchopneumonia in the stages 

 seen in our post-mortem material cannot be distinguished 

 from those attending other infectious diseases. The portions 

 of the lungs free from pneumonic processes have shown no 

 distinctive reaction to typhus. 



(d) The spleen: There is no distinctive pathology. Only 

 three spleens contain microscopic mural thrombi in the splenic 

 veins (sinuses). One spleen from a case in which there was 

 thrombosis of the superior mesenteric artery contained a 

 thrombosed artery in a follicle. One spleen with a gross in- 



