THE URINARY BLADDER 



451 



liker). These are not present in infancy. They have been interpreted 

 as vestigial prostatie tubules. 



The tunica propria resembles that of the ureter and is loosely united 

 to the muscular coat. This latter layer is formed by interlacing 

 bundles of smooth muscle. It varies much in thickness according to 

 the condition of the organ, being relatively thick when the viscus is 



A 



B 



FIG. 415. TRANSITIONAL EPITHELIUM OF DOG'S BLADDER. 



A, in the contracted condition; B, in the distended condition. (R. W. Harvey, 

 Anat. Rec., 3, 5, 1909.) 



empty and very thin when it is completely distended. In most portions 

 three indistinct layers can be obsened, a middle thick layer of circular 

 fibers, and an inner and outer longitudinal layer. The outer longitudinal 

 muscle is most distinct on the anterior and posterior surfaces of the 



organ. 



The outermost coat of the bladder consists of areolar tissue, having 

 very broad meshes; in. the lower portion of the bladder this coat blends 

 with the connective tissue of the adjacent organs. Over the fundus of 



