RENAL CIRCULATION. 393 



of capillary loops, forming a kind of tuft of fine vessels, the 

 glomerulus, which fills the cavity at the beginning of the tubules, 

 and is only covered by thin, scaly epithelial cells, and thus 

 separated from the urine. It is a singular fact, that in the renal 

 circulation the efferent vessel on leaving the glomerulus does not, 

 like most veinlets, unite with others to form a larger vein, but 

 again breaks up into capillaries, which form a dense meshwork 

 around the convoluted tubules. The blood is thence conveyed 

 to small, straight veins corresponding to the intralobular arteries. 



FIG. 174. 



Glomerulus, treated with silver nitrate, showing the endothelium. 



Another striking peculiarity of the renal vessels is that a 

 distinct set of arteries, starting from the same point as the 

 interlobular (between the cortex and medulla), pass toward the 

 centre of the gland into the pyramids. They consist of bunches 

 of straight arterioles, which lie between the straight and the 

 looped tubules. Corresponding with these straight arteries are 

 minute straight veins, which carry the blood back to the vessels 

 at the base of the pyramids. 



