474 



THE URINARY ORGANS OF THE HORSE 



duct. It lies in the sinus of the kidney, and it is funnel-shaped, but flattened dorso- 

 ventrally. The renal crest ^ (Papilla communis) projects into the outer part of 

 the pelvis in the form of a horizontal ridge with a concave free edge. The tubules 

 of the middle part of the medullary substance open on this crest into the pelvis. 

 The tubules from each end of the kidney do not open into the pelvis proper (Reces- 

 sus medius), but into two long, narrow diverticula (Recessus terminales), which 

 proceed from it toward the poles of the kidney. The wall of the pelvis consists 

 of three layers. The external fibrous coat or adventitia is continuous with the 

 supporting tissue of the kidney. The muscular coat consists of longitudinal and 

 circular fibers. The mucous coat does not cover the renal crest, nor is it continued 



Arched collecting 

 tubule 



Straight collect- 

 ing tubule 

 Distal convo- 

 luted tubule 

 Renal (Malpig- 

 hian) corpuscle 

 Proximal convo- 

 luted tubule 

 Loop of Henle 



Collecting tubule 



Arteria arci- 

 formis 



Artery of capsule 



Interlobidar 

 artery 



Capillary net- 

 work. Vas 

 offer ens 



Arteriola recta 

 spuria 



Glomerulus 



Vena arciformis 



Large collecting 

 tubule 



Papillary duct 



Fig. 380. — Diagrammatic Scheme of Urinifkrous Tubules and Blood-vessels of Kidney. 

 Drawn in part from the clescription.s of Golubew (Bohm, DavidofT, arul Huber). 



into the diverticula of the pelvis. It has a yellowish tinge, and presents numerous 

 folds. It contains glands (Glandulae pelvis renalis) which secrete the thick mucus 

 always found in the pelvis. 



Renal Tubules — The parcncliynia or proper substance of the kidney is composed of the 

 small renal or uriniferous tubules (Tuhuli renalcs), which are very clo.se together and have a 

 complicated course. Each tuhtile hejiins in a thin-walled, si)herical dilatation or capsule, wiiich is 

 invaginated to receive a tuft of looped capillaries termed a glomerulus; tiiese two structures 

 constitute a renal (or Malpighian) corpuscle; the corpuscles arc visible as minute red or dark 

 spots in the convoluted part of the cortex. Succeeding this is a short narrow neck, beyond 

 which the tubule l^ecornes wide and convoluted, forming the proximal convoluted tubule, and 

 enters the radiate portion of the cortex. It then gradually narrows and enters the intermediate 

 zone; becoming very narrow and nearly st raiglit, it descends for a variable distance in+o the medul- 

 lary sul)stancc, turns sharply upon itself, and returns to the cortex, forming thus the loop of 

 Henle, with its descending and ascending limbs. In the convoluted part of the cortex, it widens 



' The crest is the result of fusion of the papillae or apices of the pyramids in the embryo. 



