19 



obliteration of the capillaries is not complete, most of the thrombi 

 being of the tubular variety, with an open lumen in the center. 

 However, there are also seen many perfectly solid and dense, com- 

 pletely obliterating thrombi. In a fair number of places the fibrin 

 thrombi in the glomeruli are of such size that they have greatly 

 distended the vessels in the transverse diameter and stretched them 

 in a longitudinal direction, so that they have a sausage-like ap- 

 pearance. The afferent and efferent vessels frequently show an 

 incomplete thrombosis in the shape of an open fibrin reticulum. 

 This network may be continued into the main branches of the 

 afferent vessel and is occasionally found even in the finest glomer- 

 ular capillaries. Here and there, but rarely only, one sees fibrin 

 filaments which have penetrated through the vessel wall into the 

 perivascular tissue. From the afferent vessels the thrombosis can 

 sometimes be followed into the arteriae interlobulares. On the 

 other hand, thrombi are likewise found in the small interlobular 

 capillaries, into which the vasa efferentia break up. In the sub- 

 capsular glomeruli-free zone, in terminal branches of arteriae inter- 

 lobulares which do not supply glomeruli, and in interlobular capil- 

 laries of such arteries, as also in small branches of the stellate veins, 

 obliterating fibrin plugs are likewise encountered. It is thus seen 

 that almost all of the smaller vessels of the cortex are affected by the 

 process of fibrin thrombosis. However, all of the different sets of 

 vessels are not involved to the same extent, the greatest amount of 

 oljliteration being found in the glomerular capillaries and in their 

 afferent and efferent vessels. In the medulla and also in the 

 medullary rays the extent of the thrombosis is quite moderate, 

 wlien compared with that which is seen in the cortex, but here and 

 tliere one observes a thrombosed smaller vein, artery, or capillary. 

 However, the much-engorged capillary network surrounding the 

 straight tubules is almost without exception free from fibrin. 



It is difficult and often impossible to study the endothelial lining 

 in those vessels in which the thrombi are quite dense, solid, and have 

 completely obliterated the lumina. Where this is not the case — 

 where we are dealing with thinner tubular wall thrombi or with 

 fil)rin reticula, or even with solid throml)i which have become 

 soinowliat slirunken or retracted — one can generally see well-pre- 

 sorvod. apparently unchanged, vascular endothelia. In somewhat 

 larger vessels the muscle fibers present a normal appearance. 

 MalioryV special stain sbows the delicate fibers of the glomerular 



