THE CIRCULATORY SYSTEM. 



451 



brana elastica, and the lumen may be largely or wholly obliterated 

 obliterating endarteritis. The middle coat as well as the inner may Ve 

 thickened (Fig. 249). 



In larger arteries the new tissue may form beneath the endothelium 

 diffusely or in circumscribed masses, or may encircle the vessel. The 

 endothelium over the involved areas 

 may remain intact or it may prolifer- 

 ate or become fatty or necrotic. The 

 new-formed fibrous tissue of the in- 

 tima, which may contain also new elas- 

 tic fibres, ' is usually dense, having few 

 cells, and is prone to undergo fatty de- 

 generation, to become uecrotic, and 

 to disintegrate, and thus larger and 



smaller cavities filled with disintegrated tissue, fat, and cholestearin 

 crystals, may develop in the new-formed tissue (Figs. 247 and 250). 

 These are called atheromatoits cysts.* They may extend toward the lumen 

 of the vessels into which they may open, giving rise to emboli and 



FIG. 348. roxxKCTivE TISSUE FORMED IN 



THE IXTIMA IN ARTERIO-SOLEROSIS. 



FIG. 249. CHRONIC ARTERITIS. 

 Inner and middle coat thickened radial artery. 



forming rough-edged ulcers, often with undermined edges. Upon these 

 thrombi may form. In the new -formed tissue of the intima as well as 



'See Jores, Ziegler's Beitr., Ed. xxiv.. p. 458, 1898, bibliography. 



* The word atheroma is sometimes applied to the whole process of arterio-sclerosis, 

 but it would be well to linv> it to the degenerative phases which result in softening of 

 the tissues. 



