572 



URINARY APPARATUS. 



thin and elastic, the internal face of which is lined by simple epithelium that 

 readily alters ; the cells are polygonal in certain points, polyhedral in others, and 

 transparent or granular. 



The uriniferous tube has not everywhere the same dii-ection or diameter. 

 Taking it at its termination on the crest of the pelvis, and following it to its 

 origin in the Malpighian body, it is found that the tubule is at first single, 

 straight, and voluminous, but that during its course across the medullary sub- 

 stance it divides into three or four tubes, which, in their turn, subdivide in a 

 dichotomous manner. These divisions are less voluminous and straiyitt (col- 

 lected in bundles, they are the pi/ramids of Ferrein), but their diameter is 

 uniform until they reach the cortical substance ; here they bifurcate, each branch 

 becomes flexuous, and is designated the uniting or junctional tube, and is con- 

 tinued in a kind of elongated U shape — the looped or ansiform tube of Henle — 

 which descends towards the centre of the kidney. The ascending branch of this 

 ansiform tube — the diameter of which is very small — suddenly dilates on entering 

 the cortical substance, describes several bends, contracts into a narrow neck, and 



Fi? 3+0. 



SECTION OF THE CORTICAL SUBSTANCl. OF THE KIDNEY. 



A, A, Tubuli urinifen divided transversely, showing the spheroidal epitht>lium in their interior; 

 B, Malpighian capsule ; a, its afferent branch of the renal artery ; 6, its glomerulus of capillaries , 

 c, c, secreting plexus formed bj its efferent vessels , d, d, fibrous stroma. 



then opens into a Malpighian body, after having taken the name of convoluted 

 tuhp. 



The corpora Malpighiana (or capsules) are minute vesicles, the walls of which 

 possess the same structure as the uriniferous tubes ; each lodges a cluster of 

 arterial capillaries or renal glomerulus, and has two opposite openings : one com- 

 municating between the corpora and convoluted tubes, the other affording a 

 passage to the afferent and efferent vessels, which serve to irrigate a tuft of 

 capillaries forming the glomerulus of Malpighi. Between the membrane proper 

 and the glomerulus are two layers of epitheliuTn — an external continuous with 

 that of the uriniferous tube, and an internal applied directly to the glomerulus 

 and forming a kind of hood over it (lining Boivman''s capsule). 



8. Vessels and Nerves. — a. The kidney possesses a special arterg and vein, 

 remarkable for their enormous volume. 



a. The arterg (the renal) forms several branches that reach the kidney by its 

 inner border and inferior face, and divide into a certain niuuber of principal 

 vessels, which are disposed in a wavy manner on the limits of the cortical and 

 medullary substances. From them are given off branches to each of these 



