318 OSWALD S. LOWSLEY 



with many branches and whose ducts communicate with the floor 

 of the outer portion of the prostatic urethra. The section which 

 shows this arrangement of structures is reproduced diagrammatic- 

 ally in fig. 5. It was cut a little to one side of the middle line as 

 shown by the presence of part of the ejaculatory duct and its mus- 

 cular wall, and shows quite conclusively that tubules of the middle 

 and posterior lobes arise independently from the urethra and in 

 this instance could not be construed as extending in towards the 

 middle line from the lateral lobes. 



Other sections of this series show the tubules developing from 

 the prostatic furrows and sides of the urethra to form the lateral 

 lobes. Others extending from the ventral or anterior wall make 

 up the anterior lobe of the organ. In this specimen these latter 

 are quite numerous and are extensively branched. 



Fetus 19 cm. long: {twenty-two weeks) 



The bladder of this specimen is relaxed and the lumen almost 

 filled with the loose folds of mucosa pulled into it by the con- 

 traction of the muscles of the wall, which are very large in this 

 case compared to the specimens previously described. The three 

 muscular layers are clearly made out and rather larger fibers 

 than those heretofore described are seen passing from the wall of 

 the entering ureters out upon the vesical wall, forming the trigo- 

 num vesicae. The upper border of this structure is about twice 

 as thick as the bladder wall and more compactly arranged. Lower 

 down the trigone is less thick and at its middle is not as thick as 

 the bladder wall proper. The mucosa covering the trigonum vesi- 

 cae is tightly bound to it so that in relaxation of the bladder the 

 mucosa of the rest of that structure may be thrown into many 

 large folds but the trigonal mucosa does not so arrange itself. 



Extending parallel with the long axis of the lumen of the blad- 

 der just outside of the mucosa of the roof or ventral wall of that 

 structure is seen a body which arises by two small branches and 

 ends blindly in the vesical wall. It extends from the upper border 

 to the middle of the trigonum vesicae and at its upper end 

 the branches become indistinguishable from muscle bundles. 



