THE HUMAN PROSTATE GLAND 307 



it are much finer in texture than those found elsewhere and many 

 of them can be traced between the two ureters and out into other 

 portions of the trigone. 



There is a very sudden narrowing of the vesical walls at the 

 site of the developing internal sphincter and the lumen of the 

 bladder changes from an oval to a triangular shape and then into 

 a rather narrow horizontal slit with a vertical slit connecting with 

 its anterior wall as shown in fig. 2. Considerably below this it 

 becomes triangular in shape again. 



An examination of the urethra of the thirteen weeks old fetus 

 from the bladder outwards reveals the fact that two large solid 



Ventral 



Kiddle Lobe 

 Tubules 



< L\acula\o<r\i Oi/cf 

 Fig. 2 7.5 cm. human fetus. Three months. X 20. 



evaginations extend posteriorly from its floor. Outward or cau- 

 dally from these buds other larger evaginations have developed 

 forming tubules, in some of which, lumina are present. In others 

 the lumina are poorly developed, and in still others are solid (fig. 

 2). These structures, 12 in number, which are without question 

 developing prostatic tubules, are separated by a considerable 

 space from the main mass of prostatic tissue and occur directty 

 on the floor of the urethra in a position that is universally accorded 

 to the middle lobe, i.e., between the bladder and the entrance of 

 the ejaculatory ducts, and extend posteriorly to occupy a posi- 

 tion under the floor of the urethra and between the bladder and 

 ejaculatory ducts. 



