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MANUAL OF PHYSIOLOGY. 



up suddenly into numerous small branches ; these vessels then 

 form arches which run along the base of the pyramids. From 

 the latter, straight branches, called interlobular arteries, pass to- 

 wards the surface, and give off lateral branchlets which form the 

 afferent vessels to the neighboring Malpighian capsules. Within 

 the capsules the afferent arteries at once break up into a series of 

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

 erulus, which fills the cavity at the beginning of the tubules, and 



FIG. 174. 



Glomerulus, treated with silver nitrate, showing the endothelium. 



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 

 veiulets, 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 

 .-t might veins corresponding to the intralobular arteries. 



Another striking peculiarity of the renal vessels is that a dis- 

 tinct set of arteries, starting from the same point as the inter- 



