342 OSWALD S. LOWSLEY 



birth the ends of the seminal vesicles have extended back almost 

 as far as the base of the trigonum vesicae and four branches from 

 the main lumen of the organ are made out. Its walls are made up 

 of fibrous and muscular strands and are almost as thick as those of 

 the ejaculatory ducts. 



The ejaculatory ducts are the continuations of the vasa deferen- 

 tia below the entrance of the seminal vesicles. They are like the 

 vasa deferentia very large in size in the younger fetuses but grad- 

 ually become comparatively smaller in size as the other structures 

 grow larger. They pass obliquely through the posterior wall of 

 the prostatic urethra accompanied by the utricle and the surround- 

 ing stroma layers the outer fibers of which attach this cylindrical 

 mass intimately to the urethral wall by intermingling with the 

 tissue forming it. As these structures approach the lumen of the 

 urethra its floor is pushed up into a mound and its lumen con- 

 verted from a triangular into a semilunar shape. This mound, 

 called the verum montanum, is made up entirely of the ejacula- 

 tory ducts, utricle and surrounding envelopes, and gradually 

 disappears below the openings of these several structures into the 

 urethra, the stroma cells becoming intermingled with those form- 

 ing the urethral wall. 



The ejaculatory ducts pass through the posterior wall of the 

 urethra on a gradual slant in the younger fetuses but in older ones 

 their rise through the prostate is a very sudden one until they are 

 within a short distance from the lumen of the urethra, then they 

 run along parallel to its axis for a considerable distance so that 

 their course in the prostate is very much like that shown in fig. 

 10 in all of the older specimens. They open on the sides of the 

 verum montanum in such a way that there is a small area of 

 tissue over them which, if the slightest amount of pressure were 

 exerted upon it, would close them most effectively. In fact their 

 whole course in the verum montanum parallel with the axis of the 

 urethra near its lumen makes for a closure of the duct in case of 

 distention of the urethra. 



6. The urticulus prostaticus in the thirteen weeks old fetus is 

 observed as a very small lumen between the vasa deferentia. 

 It descends between them, and just below the beginning of the 



