368 



THE GENITOURINARY ORGANS. 



dymidis. According to Steiner, the epithelium of the vas deferens 

 varies. It may be provided with cilia in the lower segments, or it 

 may even be similar to that found in the bladder and ureters. 



The inner muscular layer is wanting in the ampulla of the vas 

 deferens ; here the epithelium is mostly simple columnar and pig- 

 mented. Besides the folds, there are also evaginations and tubules 

 which sometimes form anastomoses structures which may be re- 

 garded as glands. 



The seminal vesicles are also lined, at least when in a distended 

 condition, by simple, nonciliated columnar epithelium containing 

 yellow pigment. In a collapsed condition the epithelium is pseudo- 

 stratified, with two or even three layers of nuclei. The arrange- 

 ment of the epithelial cells in a single layer would therefore seem 

 to be the result of distention. The mucous membrane shows 



Epithelium. 



Outer lon- 

 gitudinal 

 muscular 

 layer. 



Fig. 297. Cross-section of vas deferens near the epididymis (human). 



numerous folds, which, in the guinea-pig for instance, present a 

 delicate axial connective -tissue stroma. Besides scanty subepithe- 

 lial connective tissue, the seminal vesicles are provided with an inner 

 circular and an outer longitudinal layer of muscle-fibers. Sperma- 

 tozoa are, as a rule, not met with in the seminal vesicles. 



The epithelium of the ejaculatory ducts is composed of a single 

 layer of cells ; the inner circular muscle-layer is very poorly devel- 

 oped. In the prostatic portion of the ejaculatory ducts the longi- 

 tudinal muscle-layer mingles with the musculature of the prostate 

 and loses its individuality. The ejaculatory ducts empty either 

 directly into the urethra at the colliculus seminalis, or indirectly 

 into the prostatic portion of the urethra through the vesicula 

 prostatica. 



1\i& prostate is a compound branched tubulo-alveolar gland. Its 



