THE UROGENITAL SYSTEM. 271 
dividing into two lateral halves. These spread out over the 
sides of the rectum, forming a broad sheet of fibres which pass 
into the walls of the rectum, among the transverse fibres of the 
latter. This muscle is covered by the caudoanalis (Fig. 
113, f), caudocavernosus (¢) (or caudovaginalis, Fig. 114, 4), 
iliocaudalis, and levator ani. 
6. Muscles Peculiar to the Male (Fig. 113).—M. levator 
scroti (7').—This is a band of fibres which passes ventrad in the 
median line from the sphincter ani externus (Z) onto the 
scrotum. Here it spreads out beneath the skin, forming 
especially a well-marked bundle in the median furrow between 
the two testes. 
M. rectocavernosus, or retractor penis (4).—A small 
bundle of fibres which arises in two parts from the ventral sur- 
face of the sphincter ani internus (#). The two parts unite into 
a single bundle which passes caudad on the middle line of the 
ventral surface of the penis; it is inserted into the corpus caver- 
nosum just proximad of the glans. The muscle is covered 
only by integument, and overlies the ischiocavernosus (7). 
M. caudocavernosus (S.-D.) (g).—A slender bundle just 
craniad of the caudoanalis (/). 
Origin on the median ventral line of the first two caudal 
vertebre. The muscle passes caudoventrad, lying between the 
levator ani and the caudorectal (¢). It divides into two bands, 
one of which is inserted into the base of the corpus cavernosum, 
while the other extends farther caudad and is inserted at the 
distal extremity of the corpus cavernosum. 
Action.—Flexes the penis (bends it backward). 
M. bulbocavernosus (accelerator urine) (/).—The two 
muscles cover the ventral surface of the penis. 
Origin of each from a median raphe, which passes from the 
bulbous portion of the urethra toward the anus. The fibres 
pass toward the distal end of the penis and have their 
Insertion into the distal half of the lateral surface of the 
corpus cavernosum penis. 
M. compressor urethre membranacee (7).—A thick layer 
of striated muscle-fibres which surrounds the urethra between 
Cowper’s gland (3) and the prostate (4). The fibres have a 
