YESICUL^E SEMINALES. 809 



VESicuLuE SEMINALES. 



The Seminal Vesicles are two lobulated membranous pouches, placed between 

 the base of the bladder and the rectum, serving as reservoirs for the semen, and 

 secreting some fluid to be added to that of the testicles. Each sac is somewhat 

 pyramidal in form, the broad end being directed backwards, and the narrow 

 end forwards towards the prostate. They measure about two and a half inches 

 in length, about five lines in breadth, and from two to three lines in thickness. 

 They vary, however, in size, not only in different individuals, but also in the 

 same individual on the two sides. Their upper surface is in contact with the 

 base of the bladder, extending from near the termination of the ureters to the 

 base of the prostate gland. Their under surface rests upon the rectum, from 

 which they are separated by the recto- vesical fascia. Their posterior extremities 

 diverge from each other. Their anterior extremities are pointed, and converge 

 towards the base of the prostate gland, where each joins with the corresponding 

 vas deferens to form the ejaculatory duct. Along the inner margin of each 

 vesicula runs the enlarged and convoluted vas deferens. The inner border of 

 the vesiculsB, and the corresponding vas deferens, form the lateral boundary 

 of a trianglar space, limited behind by the recto-vesical peritoneal fold; the 

 portion of the bladder included in this space rests on the recturn, and corres- 

 ponds with the trigonum vesicoe in its interior. 



Structure. Each vesicula consists of a single tube, coiled upon itself, and 

 giving off several irregular ctecal diverticula ; the separate coils, as well as the 

 diverticula, being connected together by fibrous tissue. When uncoiled, this 

 tube is about the diameter of a quill, and varies in length from four to six 

 inches; it terminates posteriorly in a cul-de-sac; its anterior extremity becomes 

 constricted into a narrow straight duct, which joins on its inner side with the 

 corresponding vas deferens, and forms the ejaculatory duct. 



The Ejaculatory Ducts, two in number, one on each side, are formed by the 

 junction of the duct of the vesicula seminalis with the vas deferens. Each duct 

 is about three-quarters of an inch in length ; it commences at the base of the 

 prostate, and runs forwards and upwards in a canal in its substance, and along 

 the side of the utriculus, to terminate by a separate slit-like orifice upon or 

 within the margins of the sinus pocularis. The ducts diminish in size, and 

 converge towards their termination. 



Structure. The vesiculas seminales are composed of three coats: an external or 

 fibro-cellular, derived from the recto-vesical fascia; a middle or fibrous coat, which 

 is firm, dense, fibrous in structure, somewhat elastic, and contains, according to 

 E. H. Weber, muscular fibres ; and an internal or mucous coat, which is pale, of a 

 whitish-brown color, and presents a delicate reticular structure, like that seen in 

 the gall-bladder, but the meshes are finer. The epithelium is squamous. The 

 coats of the ejaculatory ducts are extremely thin, the outer fibrous layer being 

 almost entirely lost after their entrance into the prostate, a thin layer of muscular 

 fibres and the mucous membrane forming the only constituents of the tubes. 



Vessels and nerves. The arteries supplying the vesicular seminales are derived 

 from the inferior vesical and middle haemorrhoidal. The veins and lymphatics 

 accompany the arteries. The nerves are derived from the hypogastric plexus. 



The Semen is a thick whitish fluid, having a peculiar odor. It consists of a 

 fluid, the liquor seminis, and solid particles, the seminal granules, and sperma- 

 tozoa. 



The liquor seminis is transparent, colorless, and of an albuminous composition, 

 containing particles of squamous and columnar epithelium, with oil-globules 

 and granular matter floating in it, besides the above-mentioned solid elements. 



The seminal granules are round, finely-granular corpuscles, measuring ^Vtfth 

 of an inch in diameter. 



The spermatozoa, or spermatic filaments, are the essential agents in producing 

 fecundation. They are minute elongated particles, consisting of a small flattened 



