THE EXCRETORY AND REPRODUCTIVE SYSTEMS. 183 



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 sus- 

 pended from the wall of the abdomen by a fold of in- 

 tegument 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 com- 

 posed 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 

 laterally 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. 87). 



Cowper's 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 

 a vfscid fluid of unknown function. One duct from each 

 gland opens into the urethra. 



