316 OSWALD S. LOWSLEY 



which make up the ventral lobe of the prostate. In this specimen 

 they are not nearly so numerous or so large as in the series of 

 cross sections just described. 



Fetus 16.5 cm. long: {twenty weeks) 



The bladder and prostate of a fetus five months of age cut in 

 cross sections show the musculature of the bladder wall and the 

 superimposed trigonum vesicae much more clearly than any of 

 the previous specimens described. A striking thing is the great 

 thickness of the vesical sphincter whose many layers of circular 

 fibers form a, mass about as thick as the bladder wall at its base. 

 At its upper and also outer borders the muscle fibers of the bladder 

 wall intermingle with it, thereby strengthening the vesical neck 

 to a considerable degree. The vesical orifice in this specimen 

 seems to be tightly closed. The muscular layers surrounding the 

 tubules of the prostate gland whose earliest differentiation from 

 the rest of the wall of the prostatic urethra was noted in the six- 

 teen weeks fetus, have now become quite thick and the main mass 

 of fibers are arranged circularly, although there is noted a certain 

 amount of muscular tissue extending longitudinally as described 

 by Walker. 22 



The same distribution of the prostatic gland tubules is noted 

 in this series of sections that has already been described in detail 

 in the prostate of a fetus sixteen weeks old. 



Fetus 16 cm. long: (twenty weeks) 



Sections of the bladder and prostate of a fetus five months old 

 cut in a longitudinal direction show particularly well the arrange- 

 ment of the structures at the vesical neck. The muscle bundles 

 of the bladder wall are well developed and arranged in the charac- 

 teristic manner already described. The bladder mucosa which 

 elsewhere is thrown into folds is bound tightly to the surface of 

 the trigone which is superimposed upon the vesical wall and is 



composed of muscle bundles made up of very fine fibers which 



« 



22 Walker, Johns Hopkins Hospital Bulletin, vol. 11, p. 246. 



