THE UROGENIT/fL 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. 

 H3,/), caudocavernosus (g) (or caudovaginalis, Fig. 114, //), 

 iliocaudalis, and levator ani. 



b. Muscles Peculiar to the Male (Fig. 113). M. levator 

 scroll (/). 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 (). 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 (;). 



M. caudocavernosus (S.-D.) (g). A slender bundle just 

 craniad of the caudoanalis (/). 



Origin on the median ventral line of the first two caudal 

 vertebrae. The muscle passes caudoventrad, lying between the 

 levator ani and the caudorectal (e). 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 urinae) (/). 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 urethras membranacese (;/). A thick layer 

 of striated muscle-fibres which surrounds the urethra between 

 Cowper's gland (s) and the prostate (4). The fibres have a 



