MALE PERINEUM 359 



the pubic arch ; and (4) that the space between the two 

 layers contains : 



1. The membranous portion of the urethra and its sphincter muscle. 



2. The deep transverse perineal muscle. 



3. The bulbo-urethral (Cowper's) glands. 



4. The internal .pudendal vessels, the dorsal nerves of the penis, and the 



arteries to the bulb. 



Dissection. To expose these parts, the superficial fascia of the urogenital 

 diaphragm must be raised upon one side of the body. It should be carefully 

 preserved upon the opposite side, for it is required as a landmark in the 

 subsequent dissection of the pelvis. On the side selected detach the 

 membrane from the margin of the pubic arch, and, cautiously raising it from 

 the subjacent structures, throw it medially towards the bulb. 



Pars Membranaceae Urethrse (Membranous Portion of the 

 Urethra). The canal of the urethra is subdivided for descrip- 

 tive purposes into three parts, according to the structures 

 which are in relation to its walls as it passes from the bladder 

 to its termination on the glans penis. These are (i) the 

 prostatic portion; (2) the membranous or muscular portion; 

 and (3) the cavernous portion. Each of these subdivisions 

 has a very definite relation to the urogenital diaphragm; 

 the prostatic part is placed above and posterior to both 

 layers of the diaphragm ; the membranous part is situated 

 between the two layers; whilst the cavernous portion lies 

 anterior and inferior to the diaphragm. 



Now that the superficial fascia of the diaphragm is 

 removed upon one side, the student can readily feel, with the 

 point of the finger, the staff as it lies within the membranous 

 portion of the urethra. He should examine the surroundings 

 of this canal. It is the shortest subdivision of the urethra, 

 and is distant about one inch from the symphysis' pubis. 

 Throughout its entire extent it is enveloped by the fibres 

 of the sphincter muscle, and on this account it is sometimes 

 called the muscular part of the urethra. On each side, and 

 at a lower level, is a bulbo-urethral (Cowper's) gland, whilst 

 between it and the symphysis pubis is the dorsal vein of 

 the penis which is separated from it by the transverse liga- 

 ment of the pelvis. 



M. Trans versus Perinei Profundus and M. Sphincter 



Urethrse Membranacese (O.T. Compressor Urethras Muscle). 



The deep transverse muscle of the perineum is a small 



fan-shaped muscle which lies between the fascial layers 



of the urogenital diaphragm. It has a tendinous origin 



1236 



