338 THE URINO-GENITAL SYSTEM, THE ADRENALS, ETC. 



Ba: 



tissue and involuntary muscular fibre, and lined with a mucous 

 membrane. The mucous membrane is thrown into longitudinal 

 folds, and consists, in the larger tubes, of two or three layers of 



epithelium (Fig. 218 V), that on the 

 Fig. 220. f ree surface is columnar; the deeper 



cells being rounded or polygonal. 

 The larger branches of the ureter are 

 lined with columnar epithelium (Fig. 

 21 8 VI), with small intervening cells. 

 In some parts of the branches the 

 columnar epithelium bears short cilia. 

 No glands have been found in the 

 ureter or Receptacnlum wi/tinis; in 

 liana temporaria, however, the Recep- 

 lacnlum seminis possesses large, branch- 

 ing mucous glands (Wiedersheim). 



C. The bladder. 



a. General description. The uri- 

 nary bladder (Fig. 185 1US] is closely 

 attached to the ventral wall of the 

 cloaca and' is easily distended from 

 that organ. In relation to the animal 

 it is of very large size ; in consequence 

 oi its being contracted in the middle 



it has two lobes, which may be of unequal size. The organ is 

 somewhat heart-shaped (Figs. 184 and 185), with the narrow neck 

 attached to the cloaca, into which it opens by a smaller aperture on 

 the ventral surface. The aperture is surrounded by a small fold of 

 mucous membrane. 



b. | Minute structure. The urinary bladder is bounded by a 

 thin, transparent wall, lined internally with mucous membrane, and 

 covered externally by peritoneum. 



(1) The muscular coat is formed of a network of fine bands of 

 unstriated muscular fibre (Fig. 221); it is supported and completed 

 by a connective-tissue layer, rich in connective- tissue corpuscles and 

 yellow elastic fibres. 



(2) The peritoneal coat is a single layer of endothelial cells 

 derived from the peritoneum and resting on a very thin layer of 

 subperitoneal tissue. 



Transverse section of the kidnev, 

 enlarged. 



Connective-tissue capsule. 

 Dorsal surface. 

 Renal parenchyma. 

 Ureter. 



Ventral surface. 

 Renal portal vein. 



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