4'4 



EXCRETORY URINARY PASSAGES. [sect. 1 89. 



In other cases, the increase of the stroma is more apparent than real, being 

 occasioned by the disappearance of the secreting parts. In chronic diseases 

 of the kidneys, the walls of the arteries, and of the vessels of the glomeruli, 

 are frequently thickened and impregnated with depositions of fat {Johnson). 



Fig. 173. 



§ 189. Excretory Urinary Passages. — The ureter, the pelvis, and 

 calyces of the kidney all consist of an outer fibrous coat, a layer 

 of smooth muscular fibres, and a mucous membrane. The outer 



coat, formed of ordinary connective 

 tissue and elastic fibres, chiefly of 

 the finer sorts, passes into the 

 fibrous capsule of the kidney at 

 the parts where the calyces em- 

 brace the papillae. The muscular 

 layer is very distinct in the ureters, 

 and here presents external longi- 

 tudinal, and internal transverse 

 fibres, to which, in the neigh- 

 bourhood of the bladder, other 

 longitudinal fibres are added in- 

 ternally. In the pelvis of the 

 kidney, the two muscular laminae 

 are just as thick as in the ureter; 

 but they become thinner and 

 thinner in the calyces, and ter- 

 minate where these are attached 

 to the papillae. The mucous mem- 

 brane of all these parts is thin, 

 tolerably vascular, without glands 

 or papillae, and is continued, very 

 much attenuated (ooo5'"too , oi" / 

 in diameter without epithelium), 

 upon the papillae of the kidney, where it becomes connected with 

 the internal stroma of the organ. The epithelium, covering this 

 mucous membrane, is o"02'" to o'04'" in thickness, and is in several 

 layers. It is remarkable for the varying form and size of its 

 elements, which are small and roundish cells in the deep portions, 

 cylindrical or conical (001'" to o , o2" / in length) in the middle; 

 while at the surface, the epithelium consists of roundish, polygonal 

 cells, o , oo6'" to CT04.'" in size, or of flattened plates, measuring up 

 to O'oi'". A peculiarity in these cells is the frequent occurrence 

 of two nuclei in their interior, and clear round granules, with a 



Epithelium of the pelvis of the kidney, of 

 man ; magnified 350 times. A. Isolated cells ; 

 B. the same in situ. a. anal], b. large pave- 

 ment cells; c. the same with nncleus-like 

 bodies in the interior ; d. cylindrical and co- 

 nical cells from the deeper layers; e. tran- 

 sition forms. 



