THE INFECTIOUS DISEASES. 



231 



kill the tissue cells ; others are inclined to attribute it to the pressure 

 which the new-formed cells exert on the nutritive blood-vessels. The 

 conclusions on this point which Mallory draws from a long and interest- 

 ing series of studies would indicate that a proliferation of the endothe- 

 lial cells of the blood-vessels may lead to their occlusion. This observer 

 describes the formation of occluding thrombi in the lymph vessels and 

 smaller veins. These are composed of the proliferated endothelial cells 



FIG. 112. EXDOTHELIAL CELLS IX HYPERPLASIA OF PETER'S PATCH IX TYPHOID FETER. 



These exfoliated and newly formed cells contain various foreign substances leucocytes, red blood cells, 

 fragments of nuclei, etc. Some of them are necrotic and are degenerating. A mitotic figure is seen in one. 



which have degenerated, together with 'fibrin whose formation these 

 degenerating cells induce. The accumulation of serous and fibriuous 

 exudate about these thrombi and the necrosis of tissue which may now 

 ensue, may soon be followed by necrosis of the superficial epithelium 

 and the development of ulcers. The accumulation of polyniorpho- 

 nuclear leucocytes may, according to Mallory, now occur, and, in cases 

 which go on to recovery, healing follows by the formation in the usual 

 way of granulation tissue with the ultimate restitution of the surface 

 epithelium. Mallory lays great stress upon the phagocytic nature of 

 the new-formed cells of the veins and lymph vessels. For the signifi- 

 cance of this process and other interesting details we refer to the original 

 paper. l 



The lesions which we have described are found most frequently and 

 are most pronounced in the lower part of the ileum. .They are not 

 always, however, confined to this situation. Enlarged and ulcerated 

 nodules may be found over the entire length of the ileum and even in 

 the jejunum. They may also extend downward and be found in the 

 colon, even as far down as the rectum. Similar changes may take place 

 in the appendix vermiformis. 



Mesenteric Lymph-Nodes. The mesenteric nodes undergo changes sinii- 



1 Mallory, Journal of Experimental Medicine, vol. iii., p. 611, 1898. 



