428 COMPARATIVE ANATOMY 



in length, which together with the efferent ducts forms the head of the 

 epididymis. The ductus epididymidis is the beginning of the ductus 

 deferens and, like it, lined with ciliated columnar epithelium. The 

 cilia beat towards the urethra and carry the spermatozoa to the seminal 

 vesicles where they may be temporarily stored. Layers of circular and 

 longitudinal muscles are present in the wall of the duct. At the lower 

 end of the testis the ductus loops back along the tail or cauda of the 

 epididymis, and then leaves the epididymis to join the spermatic cord. 

 As a component of the spermatic cord it passes through the inguinal canal. 

 Entering the body cavity, the ductus leaves the spermatic cord and 

 passes medially to the ureter to enter the prostate gland where it becomes 

 the ductus ejaculatorius. As it approaches the prostate, it enlarges into 

 an ampulla and is joined by the duct of the seminal vesicle. Each 

 seminal vesicle is about two inches in length and three quarters of an 

 inch in diameter, formed by an elongated tube four to five inches long 

 coiled within a connective tissue capsule. It secretes continuously an 

 alkaline mucous fluid. (Fig. 352) 



Prostate and Bulbo-urethral Glands. At the point where the ductus 

 ejaculatorius opens into the urethra, this passage is surrounded by a 

 conical mass of glandular and muscular tissue, the prostate gland. The 

 glandular portion of the prostate is formed by fifteen to thirty branched 

 tubular glands. These are embedded in connective tissue containing 

 compact masses of smooth muscle fibers. The development of the 

 prostate shows that it is a modified portion of the wall of the urethra. 

 Its alkaline mucous secretion, produced at times of sexual excitement, 

 has a stimulating effect upon the movement of spermatozoa. Character- 

 istic albuminoid concretions are formed in the alveoli of the gland. In 

 later years of life these concretions increase in size and number and 

 become calcified, so that the lumen of the urethra tends to become occluded 

 by the pressure of the prostate. Embedded in the prostate is a median 

 pouch, the prostatic utriculus or uterus masculinus, which opens by a 

 median aperture near the openings of the ejaculatory ducts. The 

 utriculus is a rudiment of the embryonic Muellerian ducts which in the 

 female become the uterus. 



The bulbo-urethral glands or Cowper's glands are tubulo-alveolar 

 glands less than half an inch in diameter, embedded in the connective 

 tissue of the urogenital diaphragm near the bulbus urethrae. Their 

 ducts open into the cavernous portion of the urethra. At times of 

 sexual excitement they secrete an alkaline mucous liquid. They appear 

 to be the first portion of the urogenital apparatus which ceases to function 

 in old age. 



The Penis. The male urethra extends into the intromittent organ, 

 the penis. Thus in the male the urethra serves both as an excretory and 



