VAS DEFERENS. 153 



cavity, it increases to nearly its natural size, and seems to gain 

 the power of executing its proper functions. — 



The Vas Deferens 



Is a very firm tube, about one line in diameter, which is not 

 perfectly cylindrical exteriorly, although the cavity formed by it 

 is so. This cavity is so small in diameter, that it will only 

 admit a fine bristle. The coats of the duct have, of course, a 

 considerable thickness. The internal coat forms a soft surface, 

 analogous to that of the mucous membranes : the external is 

 firm, and its texture resembles that of cartilage. Owing to the 

 small size of the cavity, the internal coat has not been separated 

 from the external. 



It passes upwards in the posterior part of the spermatic cord, 

 and continues with it through the abdominal ring, under and 

 exterior to the peritoneum ; soon after this it leaves the qord 

 and dips down into the cavity of the pelvis, forming a curve 

 on the side of the bladder, and proceeding backwards, down- 

 wards, and inwards. In this course it crosses the ureter, and 

 passes between it and the bladder. On the lower part of the 

 bladder the two vasa deferentia approach each other so gra- 

 dually that they appear to be nearly parallel. They proceed 

 forward between the vesiculse seminales, which are two bodies 

 irregularly convoluted, that are placed in a converging position 

 with respect to each other, and communicate with the vasa 

 deferentia. The vasa deferentia finally terminate almost in 

 contact with each other in the posterior part of the prostate 

 where they perforate the urethra. At the distance of about 

 two inches and a half from their teftnination they enlarge in 

 diameter, and become somewhat convoluted. At the posterior 

 margin of the prostate they come in contact with the anterior 

 extremities of the vesiculae seminales, and unite with them. 

 After this union they diminish in size, and become conical ; 

 and passing a short distance through the substance of the pros- 

 tate, during which they approach each other more rapidly, 

 they penetrate the urethra, so as to open in it on each side of 

 a small tubercle, called the Caput Gallinaginis, soon to be 

 described. 



