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- j... 



formis \ 



Large collecting 

 tubule 



Papillary duct ■ 



^ Artery of capsule 



Interlobular 

 artery 



Capillary net- 

 u'ork. Vas 

 offer ens 



Arleriola recta 

 spuria 



.--. Glomerulus 



Vena arciformis 



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

 Drawn in part from the descriptions of Golubew (Bohm, Davidoff, and Ruber). 



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

 folds. It contains glands (Glandulse pelvis renalis) which secrete the thick nmcus 

 always found in the pelvis. 



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

 small renal or uriniferous tubules (Tubuli renales), which are ^•ery close together and have a 

 complicated course. Each tubule begins in a thin-walled, spherical dilatation or capsule, which is 

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

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

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

 which the tubule becomes 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 straight, it descends for a variable distance into the medul- 

 lary substance, 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 embxyPf,.' . 



