OEGANS OF THE BODY. 



527 



the hilus, having previously divided, after which their subdivision is con- 

 tinued immediately within the organ. Here, after giving twigs to the 

 fibrous envelope of the organ, they pierce the latter external to the infun- 

 dibulum, each arterial twig be- 

 ing usually accompanied by a 

 large venous branch. 



In this way they advance be- 

 tween the several medullary pyra- 

 mids as far as the bases of the 

 latter. At this point both kinds 

 of vessels give off curving 

 branches, forming imperfect 

 arches among the arteries, but, 

 on the other hand, complete 

 anastomotic rings on the veins. 



From these arterial arches 

 those branches spring which bear 

 upon them the glomeruli of the 

 cortical substance (fig. 522, a). 

 They pass in general through the 

 axial portion of those blocks of 

 cortical tissue, bounded on either 

 side by medullary processes (the 

 cortical pyramids of Henle), giv- 

 ing off towards the periphery the 

 afferent vessels of the glomeruli 

 (fig. 523, , b- 512, e,f-, 522, 

 , c). 



Each of these vasa afferentia 

 subdivides at an acute angle 

 within the glomerules of man and 

 the mammalia (fig. 524, b, c 1 ), and gives origin, after coiling and twist- 

 ing there, to the vas efferens, by the union of the small branches so 



Fig. 523. 



Fig. 524. Gomerulus from the 

 pig's kidney. 



Fig. 525. 



formed (fig. 522, d; 526, d; 527). In the lower vertebrates, as for 

 instance in the adder (fig. 525), the vas afferens (a) commences to curl 



