STRUCTURE OF THE VAS DEFERENS. 289 



In adults the epithelium remains tolerably uniform through- 

 out the rest of the tube, except that many cells present a 

 distinctly marked striated basal hem or border. In the child 

 there is a great difference between the epithelium lining the 

 extra- and the intra-abdominal portions of the duct. In the 

 former the epithelium is for the most part laminated, one or 

 two layers of polyhedric and spheroidal cells lying subjacent 

 to a superficial layer of short columnar cells. Both of these 

 sets of cells contain a relatively large and usually spheroidal 

 nucleus. In that portion of the vas deferens, however, con- 

 tained in the abdomen, the epithelium resembles that of the 

 adult, the cells being beautifully defined and elongated, or 

 conical, with a border composed of rods. They are either 

 arranged in a single layer or, which is more common, they are 

 separated by fusiform cells pressing in amongst them from 

 without. The thickness of the epithelial layer in the newly 

 born child and in the extra-abdominal portion is about O02 of 

 a millimeter, and in the intra-abdominal part about 0'03 of a 

 millimeter. Near the ampulla (dilatation just above- the pros- 

 tate) of the vas deferens, the epithelium increases slightly in 

 thickness. 



The mucous la/yer succeeding to the epithelium presents two 

 or three longitudinal folds, that in the- ampulla and their 

 vicinity are not only of considerable height, but are also more 

 numerous. They are here also connected by a few transverse 

 plaits, so that hollows are formed, which some observers (Henle, 

 Ley dig) have described as glands. The mucous layer is com- 

 posed of connective tissue and elastic fibres-. The former 

 consists of decussating fasciculi of fibres, that externally run 

 chiefly in a horizontal direction, but near the epithelium are 

 more oblique, and are lost as they pass upwards or downwards. 



The elastic fibres form a tolerably dense plexus, and like the 

 fasciculi of the connective tissue of the mucous layer are 

 continuous externally with the septa of the muscular bundles, 

 and through these septa with the loose adventitia. 



The thickness of the mucous membrane depends on the 

 thickness of the muscular tunic, to which it bears an inverse 

 relation. The latter, with the exception of the first part of the 

 vas deferens, is essentially composed of two layers, arranged at 



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