ARTERY OF THE BULB LETATOR ANI. 845 



The deep perineal fascia consists of two layers, anterior and posterior ; these 

 are separated above, but united below. 



The anterior layer is continued forwards, around the anterior part of the mem- 

 branous portion of the urethra, becoming lost upon the bulb. 



The posterior layer is derived from the pelvic fascia; it is continued backwards 

 around the posterior part of the membranous portion of the urethra, and the 

 outer surface of the prostate gland. 



If the anterior layer of this fascia is detached on either side, the following 

 parts are seen between it and the posterior layer ; the subpubic. ligament .above, 

 close to the pubes ; the dorsal vein of the penis ; the membranous portion of 

 the urethra, and the muscles of the urethra ; Cowper's glands and their ducts ; 

 the pudic vessels and nerve ; the artery and nerve of the bulb, and a plexus 

 of veins. 



The Compressor Urethrse (Constrictor Urethra), surrounds the whole length of 

 the membranous portion of the urethra, and is contained between the two layers 

 of the deep perineal fascia. It arises, by aponeurotic fibres, from the upper part 

 of the ram us of the pubes on each side, to the extent of half or three-quarters 

 of an inch ; each segment of the muscle passes inwards, and divides into two 

 fasciculi, which surround the urethra from the prostate gland behind, to the 

 bulbous portion of the urethra in front ; and unite, at the upper and lower sur- 

 faces of this tube, with the muscle of the opposite side, by means -of a tendi- 

 nous raphe. 



Circular Muscular Fibres surround the membranous portion of the urethra, 

 from the bulb in front to the prostate gland behind ; they are placed imme- 

 diately beneath the transverse fibres already described, and are continuous with 

 the circular fibres of the bladder. These fibres are involuntary. 



Cowper's Glands are situated immediately below the membranous portion of 

 the urethra, close behind the bulb, and below the artery of the bulb (p. 801). 



The Pudic Vessels and Nerves are placed along the inner margin of the pubic 

 arch. 



The Artery of the Bulb passes transversely inwards, from the internal pudic 

 on the posterior margin of the triangular ligament, between the two layers of 

 fascia, accompanied by a branch of the pudic nerve. 



If the posterior layer of the deep perineal fascia is removed, and the crus 

 penis of one side detached from the bone, the under or perineal surface of the 

 Levator Ani is brought fully into view. This muscle, with the triangular liga- 

 ment in front and the Coccygeus and Pyriformis behind, closes in the outlet of 

 the pelvis. 



The Levator Ani is a broad thin muscle, situated on each side of the pelvis. 

 It is attached to the inner surface of the sides of the true pelvis, and, descend- 

 ing, unites with its fellow of the opposite side to form the floor of the pelvic 

 cavity. It supports the viscera in this cavity, and surrounds the various struc- 

 tures which pass through it. It arises, in front, from the posterior surface of 

 the body and ramus of the pubes, on the outer side of the symphysis ; poste- 

 riorly, from the inner surface of the spine of the ischium ; and between these 

 two points, from the angle of division between the obturator and recto-vesical 

 layers of the pelvic fascia at their under part ; the fibres pass downwards to the 

 middle line of the floor of the pelvis, and are inserted, the most posterior fibres 

 into the sides of the apex of the coccyx ; those placed more anteriorly unite 

 with the muscle of the opposite side, in a median fibrous raphe, which extends 

 between the coccyx and the margin of the anus. The middle fibres, which 

 form the larger portion of the muscle, are inserted into the side of the rectum, 

 blending with the fibres of the Sphincter muscles; lastly, the anterior fibres, 

 the longest, descend upon the side of the prostate gland to unite beneath it with 

 the muscle of the opposite side, blending with the fibres of the external sphinc- 

 ter and Transversus Perintei muscles, at the tendinous centre of the perineum. 



The anterior portion is occasionally separated from the rest of the muscle by 

 cellular tissue. From this circumstance, as well as from its peculiar relation 



