338 THE UEINO-GEXITAL SYSTEM, THE ADRENALS, 'ETC. 



Fig. 220. 



— : Bo- 



tissue and involuntaiy muscular fibre, and lined with a mucous 

 membrane. The mucous membrane is thrown into longitudinal 

 folds, and consists, in the larg-er tubes, of two or three layers of 



e])ithelium (Fig. 218 V), that on the 

 free surface is columnar; the deeper 

 cells being rounded or polygonal. 

 The larger branches of the ureter are 

 lined with columnar epithelium (Fig. 

 2] 8 VI), with small intervening cells. 

 In some parts of the branches the 

 columnar epithelium bears short cilia. 

 Xo glands have been found in the 

 ureter or liecepfacnhim seminis ; in 

 Hana iemporaria, however, the Hecep- 

 iacidvw. feminist possesses large, branch- 

 ing mucous glands (Wiedersheim). 



C. The bladder, 

 a. G-eneral description. The uri- 

 nary bladder (Fig. 1 85 IIB) 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 

 ol 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 ojoens by a smaller aperture on 

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

 mucous membrane. 



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

 thin, transparent wall, lined internally with mucoiis membi'ane, and 

 covered externally by peritoneum. 



(i) The muscitlar coat is formed of a network of fine bands of 

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

 by a connective-tissue layei", rich in connective-tissue corpiiscles and 

 yellow elastic fibres. 



(2) The peritoneal coat is a sing^le layer of endothelial cells 

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

 subperitoneal tissue. 



