THE SEMINAL VESICLES. 451 



layers with intermediate circular fibres. The external and middle 

 layers are thick and strong ; but the internal longitudinal stratum is 

 extremely thin, constituting not more than ith of the muscular coat. 

 The vasa deferentia of the dog, cat, and rabbit- were found by E. "Weber 

 to exhibit lively peristaltic contraction's when stimulated by means of 

 electricity. 



The surface of the lining membrane is pale ; it is thrown into three 

 or four fine longitudinal ridges, and, besides this, in the sacculated por- 

 tion of the duct, is marked by numerous finer rugre which enclose 

 irregular polyhedral spaces, resembling in this alveolar character the 

 lining membrane of the vesiculas semiuales. The epithelium is of 

 the columnar kind, and not ciliated. 



Vas aberrans. — This name was applied by Haller to a long narrow 

 tube, or diverticulum, discovered by him, and almost invariably met 

 with, which leads off from the lower part .of the canal of the epididymis, 

 or fi'om the commencement of the vas deferens, and, becoming tortuous 

 and convoluted, is rolled up into an elongated mass which extends upwards 

 for an inch or more amongst the vessels of the spermatic cord, where 

 the tube ends by a closed extremity. Its length, when it is unravelled, 

 ranges from about two to twelve or fourteen inches ; and its width in- 

 creases towards its blind extremity. Sometimes this diverticulum is 

 branched, and occasionally there are two or more such aberrant ducts. 

 Its structure appears to be similar to that of the vas deferens. Its 

 origin is probably connected with the Wolffian body of the foetus, but 

 the exact mode of its formation and its office are unknown. Luschka 

 states tliat occasionally it does not communicate with the canal of the 

 .epididymis, but appears to be a simple serous cyst. 



Organ of Giraldes. — The small body thus named is situated in the 

 front 01 the cord immediately above the caput epididymis (see Fig. 317, 

 g). It consists usually of several small irregular masses containing con- 

 voluted tubules lined with squamous epithelium, and is scarcely to be 

 recognised until the surrounding connective tissue has been rendered 

 transparent by re-agents. It has also received the name ol parepididnmis. 

 Its tubules appear to be vestiges of the glomerular part of the Wolffian 

 body. (Giraldes, in Bulletin de la Soc. Anat. de Paris, 1857, and in 

 Journal de la Physiologic, 1861, also in Proceed. Eov. Soc. vol. ix., 

 p. 231.) 



THE SEMINAL VESICLES AND EJACULATORT DUCTS. 



The vesiculsB seminales are two membranous receptacles, situated, 

 one on each side, upon the base of the bladder, between it and the rectum. 

 When distended, they form two long-shaped sacculated bodies, some- 

 what flattened on the side next the bladder, to which they are firmly 

 attached, and convex on their inferior surface ; they are widened be- 

 hind and narrow in front. Their length is usually about two inches, 

 and their greatest breadth from four to six lines ; but they vary both in 

 size and shape in different individuals, and also on opposite sides of the 

 same subject. 



Their posterior obtuse extremities are separated widely from each 

 other, but anteriorly they converge so as to approach the two vasa 

 deferentia, which run forwards to the prostate between them. AYith 



