THE GENITOURINARY APPARATUS. 259 



(a) Neck the constricted portion below the capsule, before it ter- 

 minates in the renal papillae, 



(b) Proximal convoluted tube, ? Within the cortical struc- 



(c) Spiral tttbule of Schachowa, ) ture. 



(d) Descending limb of Henle's loop, > Within the medullary struc- 



(e) Henle's loop, ) ture. 



(f) Ascending limb of Henle's loop, S 



(I) Curved tubule, 



(j) Straight collecting tubule descends through the medullary 

 structure to open by an orifice in a renal papilla. 



The straight, collecting or receiving tubes converge as they 

 descend, and unite and reunite until there are about one dozen, 

 but they vary from eight to twenty, one opening on the summit of 

 each papilla. In the cortical portion they form groups, or medul- 

 lary rays, giving the appearance of conical masses in the cortical 

 substance with their bases toward the periphery the so-called 

 pyramids of Ferrein. The tubules are composed of a basement 

 membrane, lined with pavement epithelium. In the neck the 

 epithelium becomes continuous with that of the Malpighian 

 capsule, and at the glomerule the wall is reflected upon the in- 

 closed tuft, or Malpighian corpuscle. In other situations the 

 epithelium varies much in shape and size. The renal arteries 

 subdivide at the hilum, cross the sinus, and enter the renal sub- 

 stance between the renal papillae. They terminate in the renal 

 glomerules, or Malpighian corpuscles. Each one of these re- 

 markable convolutions of capillaries is about one one-hundredth 

 of an inch in diameter and inclosed in a pouch-like dilatation 

 of the uriniferous tubules or Malpighian capsule, or capsule of 

 Bowman. The efferent vessels form, together with others, a 

 capillary net-work between and around the uriniferous tubules. 

 They are made up of three sets: (a) the plexuses around the 

 tubuli contorti ; (b) the veins beneath the capsule ; and (c) the 

 plexuses about the apices of the pyramids of Malpighi. These 

 form the vence interlcibulares, which join the vence rectce, and 

 together form the renal veins, vence pro price renales. Those in 

 the sinus unite together to form the renal vein, and open into 

 the inferior vena cava, the left crossing in front of the abdominal 

 aorta. 



The ureter commences as a compressed pouch, the pelvis. 

 Within the sinus the pelvis divides and subdivides into several 

 small funnels, or calices, each one of which receives one or two 

 projecting renal papillae. The calices, pelvis, and ureter are all 

 of the same structure, consisting of a fibrous and nnstriated mus- 

 cular and a mucous coat. The fibrous coal becomes continuous 

 with the capsule above and below in the fibrous structure of the 



