172 



ELEMENTS OF MAMMALIAN ANATOMY. 



efferentia. The epididymis is composed of a single greatly 

 convoluted tubule of which the vas defer ens is a continua- 

 tion. The latter proceeds craniad to the external ab- 

 dominal ring, which it enters to traverse the inguinal canal 

 into the abdominal cavity. It then curves caudad and 

 enters the urethra on its dorsal aspect in the region of the 

 prostate gland. 



The inguinal canal begins with the external abdominal 

 ring, which is an opening in the tendon of the external 



oblique muscle, and ends with the 

 internal abdominal ring, which is an 

 opening in the fascia of the trans- 

 versalis muscle (Fig. 51). By acci- 

 dent, a fold of the small intestine 

 in man sometimes descends through 

 the inguinal canal, which condition 

 is known as hernia or rupture. 



The penis is a cylindrical pointed 

 body about three centimeters long 

 when in repose. It is composed of 

 two kinds of tissues arranged in three bundles. The corpus 

 spongiosum is the median ventral bundle, extending 

 throughout the length of the organ, and at the end forms 

 the glans or head. The two dorsal lateral bundles are the 

 corpora cavernosa. They form the greater part of the penis 

 proximad of the glans, and by diverging somewhat before 

 their attachment on either side to the pubis and ischium 

 form the crura. The penis is suspended from the wall of 

 the abdomen by a fold of integument inserted at the base 

 of the glans, and forming the prepuce. The latter is a 

 free projection of skin covering the glans. In the midst 

 of the penis is a small bone. The penis is the organ of 

 copulation, and is composed of a spongy mass of elastic and 

 muscular fibers richly supplied with highly distensible 

 blood-vessels which when filled render the organ erect. 



FIG. 91. SPERMATOZOA 

 OR MALE GERM CELLS. 

 Xsoo. 

 h, Head; t, tail. 



