354: 



HANDBOOK OF PHYSIOLOGY. 



In the pyramids the tubes are chiefly straight dividing and diverg- 

 ing as they ascend through these into the cortical portion ; while in the 

 latter region they spread out more irregularly, and become much 

 branched and convoluted. 



Tubuli Uriniferi. The tubuli uriniferi (Fig. 243) are composed of 

 a nearly homogeneous membrane, and are lined internally by epithelium. 

 They vary considerably in size in different parts of their course, but are, 

 on an average, about ^ of an inch in diameter, and are found to be 

 made up of several distinct sections which differ from one another very 

 markedly, both in situation and structure. According to Klein, the fol- 

 lowing segments may be made out: (1) The MalpigUan corpuscle (Figs. 

 244, 245), composed of a hyaline membrana propria, thickened by a 

 varying amount of fibrous tissue, and lined by flattened nucleated epi- 



FIG. 242. 

 FIG. 242. Plan of a longitudinal section through the pelvis and substance of the right kidney, 



lecting into calyces; e, e, section or tne narrow part or two pyramids near tne calyces; p, 

 enlarged divisions of the ureter within the kidney; u, the ureter; s, the sinus; h, the hilus. 



FIG. 243. A. Portion of a secreting tubule from the cortical substance of the kidney. B. The 

 epithelial or gland-cells, x 700 times. 



thelial plates. This capsule is the dilated extremity of the uriniferous 

 tubule, and contains within it a glomerulus of convoluted capillary 

 blood-vessels supported by connective tissue, and covered by flattened 

 epithelial plates. The glomerulus is connected with an efferent and an 

 afferent vessel. (2) The constricted neck of the capsule (Fig. 244, 2), 

 lined in a similar manner, connects it with (3) The Proximal convoluted 

 tubule, which forms several distinct curves and is lined with short 

 columnar cells, which vary somewhat in size. The tube next passes al- 

 most vertically downwards, forming (4) The Spiral tubule, which is of 

 much the same diameter, and is lined in the same way as the convoluted 

 portion. So far the tube has been contained in the cortex of the kidney; 



