REPRODUCTION 507 



form about 20 vasa recta (b) , and these pass out of the gland at its 

 upper end, as the vasa efferentia (d), which become coiled up into 

 conical masses, the coni vasculosi; these, when unrolled, are tubes 

 from 15 to 20 cm. (6-8 inches) in length; they taper somewhat 

 from their commencements at the vasa efferentia, where they are 

 0.5 mm. ($ inch) in diameter, to the other end where they ter- 

 minate in the epididymis (e, e, Fig. 149). The latter is a narrow 

 mass, slightly longer than the testicle, which lies along the posterior 

 side of that organ, near the lower end of which it passes (g) into the 

 vas deferens, h. If the epididymis be carefully unravelled it is 

 found to consist of a tube about 6 meters (20 feet) in length, and 

 varying in diameter from 0.35 to 0.25 mm. (y 1 ^ to -g 1 ^ inch) . 



The vas deferens (h, Fig. 149) commences at the lower part of 

 the epididymis as a coiled tube, but it soon ceases to be convo- 

 luted and passes up beneath the skin covering the inner part of 

 the groin, till it gets above the pelvis and then, passing through 

 the abdominal walls, turns inwards, backwards, and downwards, 

 to the under side of the urinary bladder, where it joins the duct 

 of the seminal vesicle; it is about 0.6 meter (2 feet) in length and 

 2.5 mm. (yV inch) in diameter. Its lining epithelium is ciliated. 



The vesiculce seminales, two in number, are membranous recepta- 

 cles which lie, one on each side, beneath the bladder, between it and 

 the rectum. They are commonly about 5 cm. (2 inches) long and a 

 little more than a centimeter wide (or about 0.5 inch) at their broad- 

 est part. The narrowed end of each enters the vas deferens on its 

 own side, the tube formed by the union being the ejaculatory duct, 

 which, after a course of about an inch, enters the urethra near 

 the neck of the bladder. In some animals the vesiculce seminales 

 form a liquid which is added to the secretion of the testis. In man 

 they appear to be merely reservoirs in which the semen collects. 



The prostate gland is a dense body, about the size of a large 

 chestnut, which surrounds the commencement of the urethra; 

 the ejaculatory ducts pass through it. It is largely made up of 

 fibrous and unstriped muscular tissues, but contains also a num- 

 ber of small secreting saccules whose ducts open into the urethra. 

 The prostatic secretion though small in amount would appear to 

 be of importance: at least the gland remains undeveloped in per- 

 sons who have been castrated in childhood; and atrophies after 

 removal of the testicles later in life. 



