346 



THE ANATOMY OF THE HORSE 



dilatation — Boivman's capsule. Boivman's capsule surrounds a clue-like 

 tuft of capillary vessels called the glomerulus, and the whole constitutes 

 a malpighian body. It is more natural, but less simple at first, to 

 regard the tube as beginning, not at the crest of the pelvis, but at 

 Bowman's capsule. The student should mentally work it out in that 



direction for himself. The 

 uriniferous tubules consist of 

 a basement membrane with 

 an epithelial lining. In the 

 convoluted and intermediary 

 tubes the cells are irregularly 

 columnar, but their outlines 

 are obscure; in the descending 

 limb of Henle's tube (nearest 

 the capsule of Bowman) the 

 cells are flattened ; and else- 

 where the cells lining the 

 tubes are cubical or columnar. 

 The Renal Vessels. The 

 renal artery divides into a 

 number of branches which 

 penetrate the kidney near the 

 hilus. Arriving between the 

 cortex and the boundary layer, 

 the arteries divide and anasto- 

 mose to form a series of arches 

 from which both cortical and 

 medullary vessels arive. 



The cortical or interlobular 

 arteries are larger and more 

 numerous than those for the 

 medulla. They pass directly 

 outwards towards the surface 

 of the kidney, giving off lateral 

 branches — the vasa afferentia 

 — to Bowman's capsule, and terminal branches to the fibrous coat of 

 the kidney. Each vas afferens pierces Bowman's capsule, and resolves 

 itself into the glomerulus, or capillary tuft. From this again the blood 

 is led out of Bowman's capsule by the vas eferens. The vasa efferentia 

 again resolve themselves into capillaries, and these form a network 

 among the convoluted tubes. From this intertubular capillary net- 

 work, small veins arise and pass to join the interlobular veins, running 

 alongside the arteries. These interlobular veins begin at the surface of 

 the kidney by the convergence of a number of minute veins from the 



Fig. 49. 



Vessels of the Kidneys, and Uriniferous 

 Tubules (modified from Turner). 

 1. Papillary duct; 2. Collecting tube; 3. Inter- 

 mediary tube ; 4. Looped tube of Henle ; 5. Con- 

 voluted tube ; 6. Bowman's capsule ; A. Segment of 

 artery forming renal arch ; B. Interlobular artery ; 

 C. Afferent vessel of glomerulus ; D. Efferent vessel 

 of the same ; E. Glomerulus ; F. Plexus formed by 

 vasa efferentia ; G. Arteriole rectse ; H. Interlobular 

 vein. 



