2o6 ELEMENTS OF MAMMALIAN ANATOMY 



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 sus- 

 pended 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. 



The prostate gland surrounds the urethra dorsally and lat- 

 erally about two or three centimeters from the bladder. This 

 gland secretes a milky fluid which is poured into the urethra 

 through many ducts, during copulation, and serves as a medium 

 for the spermatozoa (Fig. loi). 



Cowper's bulbo-urethral glands are two in number, about 

 the size of a pea, and lie in the angles formed by the urethra 

 and the crura of the corpora cavernosa. These glands secrete 

 an alkaline viscid fluid of unknown function, "but which may 

 be to neutralize any acidity of the urethra which might in- 

 hibit the activity of the spermatozoa" (McMurrich). One 

 duct from each gland opens into the urethra. 



REMARKS ON THE MAMMALIAN UROGENITAL SYSTEM 



The urogenital system is subject to some variations in the 

 different orders of Mammalia. In the Ornithodelphia, the 

 mammary glands are devoid of teats and the oviducts corre- 

 sponding to the Fallopian tubes and horns of the uterus do not 

 unite in the median line to form the body of the uterus, but 

 unite with the urethra, forming the urogenital canal. The 

 latter opens into an enlarged terminal portion of the rectum, 

 called the cloaca. The ureters also open directly into the 

 cloaca, so that there is but one external opening for the genital 



