332 OSWALD S. LOWSLEY 



previous specimens and which is shown in fig. 10. In this as 

 in the other specimens studied the verum montanum is observed 

 to be composed of the ejaculatory ducts, utriculus prostaticus 

 and their walls. The ejaculatory ducts run for a shorter dis- 

 tance in the verum montanum in this than in the prostates previ- 

 ously discussed, finally opening on the lateral walls of that struc- 

 ture in the characteristic way already described. 



The utriculus prostaticus is found in the tip of the verum mon- 

 tanum extending only a short distance before it opens into the 

 urethra in the midline, and in this case has a very large wide open- 

 ing above the mouths of the ejaculatory ducts which is not the 

 usual arrangement, as in all of the other specimens studied its 

 mouth has been below those of the ejaculatory ducts. There 

 have not been found in this or in any of the other prostates studied 

 either an ejaculatory duct or a prostatic tubule opening into the 

 utriculus prostaticus. 



DISCUSSION 



1. The bladder of a fetus ten weeks old consists of a cylindrical 

 tube composed of embryonic connective tissue. Near its base 

 it is joined by the two ureters which pass through its wall and 

 fibers from which are superimposed upon the bladder wall to form 

 the trigonum vesicae. There is no tissue resembling muscle 

 present and the future site of the vesical sphincter is not dis- 

 tinguishable except by the change in the size and shape of the 

 lumen. 



At the thirteenth week the muscular development has begun 

 and is observed as circular interlacing and longitudinal strands of 

 tissue that take on a deeper pink color than does the connective 

 tissue which still forms the major portion of the bladder wall. 

 The entire base of the bladder is thicker than any other portion 

 of its circumference while the superimposed trigonum vesicae 

 and the wall under it are five times as thick as the anterior wall. 

 The muscle fibers observed in the trigonum are traced between 

 the two ureters and down on the rest of the trigone. They are 

 finer in texture than the muscle fibers in the bladder wall. The 

 site of the internal sphincter is marked by a sudden narrowing in 



