542 THE TISSUES, 



sicae) ; and 2, an external layer of parallel longitudinal fasciculi (the 

 detrusor urince). 



The mucous membrane is pale, smooth, and rather thick, except 

 where the vesical triangle is situated ; and most vascular at the fun- 

 dus and the neck of the bladder. Its nerve-fibres are principally 

 confined to the same parts, are dark-bordered, and both fine and of 

 medium size. Its epithelium generally approaches the compound 

 scaly kind, and, like that of the pelvis of the kidney, is remarkable 

 for the diversity in form and size, of its cells the deeper being 

 usually elongated, and the superficial rounded, polygonal, or flat- 

 tened. A conoidal epithelium, however, exists near the urethra 

 and the orifices of the ureters. The corium is level (presenting no 

 papilla), and shows isolated or aggregated simple racemose mucous 

 glands in the neck of the bladder and towards the fundus. These 

 are -g J F to -fa of an inch in diameter, and their orifices are g j^ to 

 2 ^ of an inch. They have a conoidal epithelium. In pathologi- 

 cal conditions these are sometimes enlarged and filled with whitish 

 mucous plugs. ( Virchow.) There is an abundant submucous layer 

 of areolar tissue, except over the vesical triangle; and which is 

 thrown into numerous folds when the bladder contracts. 



3. The ureters, including also the pelvis and the calices of the 

 kidney, are composed of an external fibrous coat, a middle mus- 

 cular coat, and a mucous membrane. 1. The fibrous coat is com- 

 posed of areolar tissue, and where the calices surround the papillce, 

 is continuous with the fibrous coat of the kidney. 2. The muscular 

 , tunic consists of an external longitudinal, and an internal trans- 

 verse layer of smooth fibres; longitudinal fibres being also added 

 to the inner layer towards the bladder. The two muscular layers 

 are as thick in the pelvis of the kidney as in the ureters lower 

 down ; becoming thinner in the calices, and ceasing where the latter 

 are inserted into the papillae. 3. The mucous membrane is thin 

 throughout, tolerably vascular, without glands or papillae, and is 

 continued upon the renal papillae. Its epithelium is the compound 

 scaly variety like that of the bladder, and is g j to -g^ of an inch 

 thick. The cells frequently contain two nuclei. 



Structure of the Kidney. 



The kidney is made up of 8 to 15 lobules (pyramids of Malpighi), 

 each inclosed in an investment of areolar tissue; and which are all 

 invested together by the fibrous capsule of the kidney. Outside of 



