THE HUMAN PROSTATE GLAND 315 



Fetus 12 cm-, long: {sixteen weeks) 



A series of sections cut in the longitudinal direction through the 

 bladder and prostatic urethra of a fetus four months of age shows 

 the arrangement of the various structures in a very striking manner. 

 The smooth muscle of the bladder wall stains very deeply and is 

 bound in place by the lighter staining connective tissue. The 

 mucous membrane of the bladder and the submucous tissue is 

 thrown into folds and finger-like projections into the vesical lumen 

 except over the trigonum vesicae where it is tightly adherent to 

 the muscle forming this structure. The trigonum vesicae is made 

 up of muscular fibers which are finer in texture, more tightly 

 bound together, and have lighter staining characteristics than the 

 rather heavy, loose, deeply staining muscle bundles of the bladder 

 wall proper upon which it is superimposed. The trigonal tissue 

 extends down through the vesical neck and becomes lost among 

 the muscle fibers of the prostatic urethra. The sphincter of the 

 bladder appears as a large oval mass of circular fibers which sur- 

 round the neck of the bladder and are quite distinct from the sur- 

 rounding structures. There is a sharp line of differentiation 

 around its lower part, while above some fibers from the trigone 

 and vesical wall mingle with the fibers of the sphincter attaching 

 it intimately to them. 



The distribution of the tubules of the prostate gland is similar 

 to that just described in the cross sections of the bladder and pros- 

 tatic urethra of a fetus at this age. On the floor of the urethra 

 just below the vesical sphincter several small evaginations repre- 

 sent the developing glands of Albarran. The middle lobe of 

 the prostate is composed of several large tubules with a number of 

 branches which extend back posterior to the sphincter and ante- 

 rior to the ejaculatory ducts. The lateral lobes are somewhat 

 larger than the middle lobe, being composed of numerous tubules 

 with many large branches. The posterior lobe tubules are seen 

 extending from the floor of the urethra below or outerward from 

 the entrance of the ejaculatory ducts to a position behind them. 

 On the roof or ventral wall of the urethra are found the tubules 



