THE HUMAN PROSTATE GLAND 341 



tubules. The greatest change in this structure is noted in the 

 new-born in which the anterior lobe is made up of two insignifi- 

 cant tubules situated on the anterior part of the gland at its middle 

 as shown in fig. 10. 



The subcervical glands of Albarran are seen to occur in the 

 specimen sixteen weeks of age and in all of the older ones. Their 

 number varies from eight to nineteen, the average in the four 

 series being twelve. 



The subtrigonal glands are not found until the twenty-second 

 week and they are in all cases few in number, varying from four 

 to nine, the average in three specimens being six. 



5. The vasa' deferentia descend behind the posterior surface of 

 the bladder, each one being situated near the ureter. Lower 

 down they gradually approach one another and in the earlier 

 stages become contiguous behind the middle of the trigonum vesi- 

 cae. In their descent they increase enormously in size, so that 

 under the internal sphincter of the bladder they with their envel- 

 oping tissue are larger than the commencement of the urethra 

 with its surrounding tissue. At this point the lumen of the vasa 

 deferentia have widened considerably denoting the first appear- 

 ance of the ampullae. These structures remain comparatively 

 large until the sixteenth week after which they become relatively 

 very much smaller. 



The seminal vesicles originate in the thirteenth week. They 

 appear first as an evagination lateralward from each vasa deferens 

 being covered by the same tissue that envelops the latter struc- 

 tures. They grow backwards and laterally consisting of a main 

 part which is convoluted and from which rather numerous, short, 

 convoluted branches grow out as described by Pallin. 23 In the 

 further development of these structures the opening into the ejacu- 

 latory ducts becomes comparatively smaller and its component 

 parts become larger and more tortuous. In the thirty weeks old 

 fetus they are found back under the trigonum vesicae at about its 

 middle point and communicate with the vasa deferentia deeply 

 in the base of the prostate to form the ejaculatory ducts. At 



23 Gustaf Pallin, Archiv fur Anatomie und Physiologie, 1901. 



