THE URINARY ORGANS. 



333 



rays and in the cortical pyramids. The meshes of the capillary net- 

 works distributed throughout the medullary rays are considerably 

 longer than those of the networks supplying the cortical pyramids 

 and labyrinth, the 'latter being quadrate in shape. The glomeruli 

 nearest the renal papillae give off longer vasa efferentia which extend 

 into the papillary region of the Malpighian pyramids (arteriolae 

 rectas spurise) and form there capillaries which ramify throughout 

 the papillae with oblong meshes. 



Artery of 

 capsule. 



Arched collecting . 

 tubule. "'*--.. 



Straight collect- 

 ing tubule. ---- 



Distal convoluted 

 tubule. 



Malpighian cor- 

 puscle. 



Proximal convo- > 

 luted tubule. "/*, 

 Loop of Henle. w 



Collecting tubule. 



Arteria arcuata. ... \ 



\ --- Glomerulus. 



Vena arcuata. 



Large collecting 

 tubule. 



Papillary duct. 



Fig. 269. Diagrammatic scheme of uriniferous tubules and blood-vessels of kidney. 

 Drawn in part from the descriptions of Golubew. 



Arterial retia mirabilia also occur in the course of the vasa 

 afferentia between the intralobular arteries and the glomeruli, but 

 nearer the latter. Each is formed by the breaking down of the small 

 afferent vessels into from two to four smaller branches, which then 

 reunite to pass on as a single vessel. In structure these retia differ 

 greatly from the glomeruli in that here the resulting twigs are not 

 capillaries and have nothing to do with the secretion of urine 

 (Golubew). 



From the vasa afferentia arterial twigs are occasionally given 



