THE REPRODUCTIVE SYSTEM. 6i5 



urethra. It is somewhat chestnut-shaped. It measures an inch and a 

 half in breadth, and an inch and a quarter long, and half an inch in 

 thickness. 



Structure. The prostate is made up of small compound tubular 

 glands imbedded in an abundance of muscular fibres and connective 

 tissue. 



The glandular substance, which is nearly absent from the front part 

 of the organ, consists of numerous small saccules, opening into elongated 

 ducts, which unite into a smaller number of excretory ducts. The acini 

 of the upper part of the prostate, are small and hemispherical; while in 

 the middle and lower parts the tubes are longer and more convoluted. 

 The acini are of two kinds, namely, those (a) lined with a single layer of 



FIG. 435. Dissection of the base of the bladder and prostate gland, showing the vesiculse semi- 

 nales and vasa deferentia. a, lower surface of the bladder at the place of reflexion of the peri- 

 toneum ; 6, the part above covered by the peritoneum ; i, left vas def erens, ending in e, the ejacula- 

 toryduct; the vas def erens has been divided near z, and all except the vesical portion has been 

 taken away; s, left vesicula seminalis joining the same duct; s, s, the right vas def erens and right 

 vesicula seminalis, which has been unravelled; p, under side of the prostate gland; m, part of the 

 urethra; u, u, the ureters (cut short) ; the right one turned aside. (Haller.) 



thin and long columnar cells, each with an oval nucleus in outer part of 

 wall; and those (b) acini resembling the foregoing, but with a second 

 layer of small cortical, polyhedral, or fusiform cells between the mem- 

 brana propria and the columnar cells. The ducts, twelve to twenty in 

 number, open into the urethra. They are lined by a layer of columnar 

 cells,, beneath which is a layer of small polyhedral cells. 



The tunica adventitia consists of dense fibrous tissue of two layers, 

 between which is situated a plexus of veins. Larger vessels pass into the 

 interior of the organ, to form a broad-meshed capillary system. Nerves 



