1956 



HUMAN ANATOMY. 



Fibrous coat 



Lumen 



Utricle (Fig. 1632). In rare cases the ducts of the two sides may join before reach- 

 ing the urethra and communicate with the latter by a common aperture, or they may 

 open independently into the prostatic utricle. In the descent ot the duct the lumen 

 of its upper and middle thirds is modified by a series of four or five diverticula of de- 

 creasing size ( Felix j. At such levels the usual oblique oval outline of the canal is 

 amplified by the irregular dilatations. 



Structure of the Spermatic Duct. — The vas deferens is distinguished by the 

 conspicuous thickness of its wall (from 1-1.5 mm.) that encloses a relatively narrow 

 lumen (.5-7 mm.) and confers upon the canal its characteristic hard, cord-like feel. 

 The wall consists of three coats, the mucous, muscular, and fibrous (Fig. 1664). The 



mucous coat is clothed with 

 Fig. 1664. epithelium which in the vi- 



cinity of the testicle and for 

 an uncertain distance beyond 

 resembles that lining the duct 

 of the epididymis, consist- 

 ing of an imperfect double 

 layer of tall, columnar cili- 

 ated cells. Throughout the 

 greater part of the duct, how- 

 ever, the cells are lower and 

 , without cilia and contain 

 numerous particles of pig- 

 ment. The tunica propria 

 possesses a dense felt-work 

 ' of elastic fibres intermingled 

 with bundles of fibrous tissue. 

 The robust muscular coat 

 (from .8-1.2 mm. in thick- 

 ness) constitutes approxi- 

 mately four-fifths of the en- 

 tire wall, and consists of pale 

 fibres arranged as an outer 

 longitudinal, a middle circu- 

 lar, and an inner longitudinal 

 layer, the latter being less 

 well developed than the outer and middle strata. The external Jibj'ous coat that 

 invests the muscular tunic is thin and serves to connect the spermatic duct with the 

 surrounding structures. 



In its general structure the ampulla corresponds with the vas deferens, the walls 

 of this part of the duct, however, possessing a much thinner muscular coa,t, in which 

 the inner longitudinal layer is wanting, and a mucosa modelled by numerous ridgel 

 and depressions (Fig. 1663) and covered with a single layer of low, columnar, non- 

 ciliated epithelial cells. 



The ejaculatory duct likewise possesses a structure essentially the same as in 

 other parts of the spermatic canal. Its walls, however are thinner than those of the 

 ampulla, this reduction being due to the diminished thickness and incompleteness of 

 the muscular coat, which on nearing the urethra becomes attenuated and mingled with 

 fibrous tissue. In some places the epithelium of the duct consists of a single and in 

 others of a double layer of columnar cells until within a short distance from the termi- 

 nation of the canal, where it assumes the transitional character of the epithelium 

 lining the prostatic urethra. * 



Outer 

 longitudinal 

 muscle 

 Circular 

 muscle 

 Inner 

 longitudinal- 

 muscle 



Mucous 

 membrane 



X 



Cross-section of vas deferens, y 20. 



THE SEMINAL VESICLES. 



The seminal vesicles (vesiculae seminales) are two sacculated appendages of the 

 vasa deferentia that lie behind the bladder and in front of the rectum. Flattened from 

 before backward, their general shape is pyriform, with the larger ends, or bases, 

 directed upward and outward, the long axes converging towards the mid-line as the 



