220 MUSCLES OF THE PERINEUM. 



fascia is then to be removed to the same extent, exposing the superficial 

 perineal fascia. This layer is also to be turned aside, when the muscles 

 of the genital region of the perineum will be brought into view. 



The ACCELERATORES TIRING (bulbo-cavernosus) arise from a tendinous 

 point in the centre of the perineum and from the fibrous raphe of the two 

 muscles. From these origins the fibres diverge, like the plumes of a pen 

 the posterior fibres to be inserted into the ramus of the pubes and ischium 

 the middle to encircle the corpus spongiosum, and meet upon its upper 

 side ; and the anterior to spread out upon the corpus cavernosum o$ each 

 side, and be inserted, partly into its fibrous structure, and partly into the 

 fascia of the penis. The posterior and middle insertions of these muscles 

 are best seen, by carefully raising one muscle from the corpus spongiosum 

 and tracing its fibres. 



Relations. By their superficial surface with the superficial perineal 

 fascia, the dartos, the superficial vessels and nerves of the perineum, and 

 on each side with the erector penis. By their deep surface with the corpus 

 spongiosum and bulb of the urethra. 



The ERECTOR PENIS (ischio-cavernosus) anses from the ramus and tu- 

 berosity of the ischium, and curves around the root of the penis, to be in- 

 serted into the upper surface of the corpus cavernosum, where it is con- 

 tinuous with a strong fascia which covers the dorsum of the organ, the 

 fascia penis. 



Relations. By its superficial surface with the superficial perineal fascia, 

 the dartos, and the superficial perineal vessels and nerve. By its deep 

 surface with the corpus cavernosum penis. 



The COMPRESSOR URETHJE (Wilson's and Guthrie's muscles), consists 

 of two portions ; one of which is transverse in its direction, and passes in- 

 wards, to embrace the membranous urethra ; the other is perpendicular, 

 and descends from the pubes. The transverse portion, particularly de- 

 scribed by Mr. Guthrie, arises by a narrow tendinous point, from the upper 

 part of the ramus of the ischium, on each side, and divides into two fasci- 

 culi, which pass inwards and slightly upwards, and embrace the membra- 

 nous portion of the urethra and Cowper's glands. As they pass towards 

 the urethra, they spread out and become fan-shaped, and are inserted into 

 a tendinous raphe upon the upper and lower surfaces of the urethra, ex- 

 tending from the apex of the prostate gland, to which they are attached 

 posteriorly, to the bulbous portion of the urethra, with which they are con- 

 nected in front. When seen from above, these portions resemble two fans, 

 connected by their expanded border along the middle line of the mem- 

 branous urethra, from the prostate to the bulbous portion of the urethra. 

 The same appearance is obtained by viewing them from below. 



The perpendicular portion* described by Mr. Wilson, arises by two ten- 

 dinous points from the inner surface of the arch of the pubes, on each side 

 of, and close to, the symphysis. The tendinous origins soon become 

 muscular, and descend perpendicularly, to be inserted into the upper fas- 

 ciculus of the transverse portion of the muscle ; so that it is not a distinct 

 muscle surrounding the membranous portion of the urethra, and support- 



Mr. Tyrrell, who made many careful dissections of the muscles of the perineum, 

 did not observe this portion of the muscle ; he considers Wilson's muscle (with some 

 other anatomists) to be the anterior fibres of the levator ani, not uniting beneath tha 

 urethra, as described by Mr. Wilson; but inserted into a portion of the pelvic fascia 

 iuutsd, between the prostate gland and rectum, the recto-vesical fascia. 



