968 GENERATIVE APPARATUS. 



lying on a thin fibrous tunic ; while beyond, there is observed a stratified ciliated 

 epithehum, a proper membrane, two layers of unstriped fibres — circular and 

 longitudinal — and also a fibrous tunic. The thickness of the muscular layers 

 increases from before to behind. 



The epididymis is enveloped by a fibrous membrane and the tunica vaginalis 

 propria. It receives its arteries and nerves from the same sources as the 

 testicle. 



Vas Deferens. — This duct is about the thickness of a goose-quill, and is at 

 first flexuous, then straight. It lies parallel with, but behind and to the inner 

 side of, the spermatic vessels, as far as the opening of the internal ring ; passing 

 through this opening, it enters the pelvic cavity, and crosses obliquely the ureter 

 and o])literated cord of the umbilical artery. It is then inflected backwards above 

 the l)ladder, suddenly dilates {bulbous portion), and is prolonged as far as the 

 neck of that reservoir, where it terminates, after having penetrated beneath the 

 prostate gland by a sudden constriction, at the origin of which, and outwardly, ■ 

 the vesicula seminalis opens, and is continued by the ejaculatory ducts. 



It may, therefore, be divided into four portions — a testicular, funicular, 

 itujimuil, and pelvic. 



The vas deferens is sustained in the vaginal canal by a very short serous fold 

 — a dependency of the fr^enum — the two layers of which envelop the spermatic 

 vessels, within and behind which this duct is situated. In the abdominal cavity, 

 it is fixed by the prolongation of this serous duplicature. Its dilated or pelvic 

 portion is in contact, superiorly, with the vesiculfe seminales, and is finally united 

 to its dilated homologue of the opposite side — which it has been gradually 

 approaching — by means of a triangular peritoneal fold, that comprises between 

 its two layers a small club-shaped cavity — the prostatic utricle, which will be 

 alluded to again. 



The calibre of the vas deferens is very small in its vaginal and abdominal 

 portions, but is greater towards the pelvic dilatation, where the wall of the duct 

 offer a well-marked areolated disposition (ampullw). 



Structure. — The vas deferens is formed, internally, by a very fine mucoids 

 membrane covered with cylindrical epithelium, and to this is added, externally, a 

 contractile and 2i fibrous tunic. The contractile layer is formed of three planes of 

 smooth muscular fibres ; the deep and superficial planes have longitudinal, and 

 the middle circular fibres. It is, proportionately, very thick at the dilated por- 

 tion of the duct, and it is to its great density that the vas deferens owes its con- 

 sistence as a hard, rigid cord. The mucous membrane of the pelvic dilatation 

 offers a large surface, being inflected into all the depressions, but it has no 

 follicles ; the cells of its epithelium have special granules which give a dark 

 colour to the membrane. 



2. The Vesicula Seminales and Ejaculatory Ducts (Fig. 522). 



The vesiculce seminales are two oval pouches, the volume of which varies with 

 their contents ; they are placed in the pelvic cavity, above the bladder and the 

 vas deferens. 



Eaph vesicula has a middle portion and tivo extremities. The middle portion 

 is enveloped by a loose abundant connective tissue, and is in relation with the 

 rectum above, and below with the bladder and vas deferens. 



The anterior extremity is the largest, and forms a rounded cui-d^-sac, covered 



