PERINEUM. 



929 



The transversalis perinei artery is of small 

 size; it springs from the internal pudic, a little 

 anterior to the source of the superficial perineal 

 artery, but these two vessels not unfrequently 

 arise by a single common trunk. The trans- 

 versalis perinei artery passes through the obtu- 

 rator fascia, and often perforates the base of 

 the triangular lisjament of the urethra ; it quickly 

 becomes superficial, applying itself to the cuta- 

 neous surface, and running usually near the 

 posterior edge of the transversus perinei mus- 

 cle, it thus gains the central tendinous point 

 of the perineum, where it anastomoses vvitli 

 the inferior hemorrhoidals from behind, the 

 transversalis and superficialis perinei arteries 

 from the opposite side, and with the neigh- 

 bouring superficial perineal. This vessel is 

 accompanied by two veins and by one or more 

 branches of the superficial division of the 

 pudic nerve. 



The accelerator urinse muscle (the ejaculator 

 seminis of some anatomists, the bulbo-caver- 

 nosus of others) extends from the central ten- 

 dinous point of the perineum forwards along 

 the urethra, being identified with the correspon- 

 ding muscle of the opposite side in a raphe 

 which occupies the middle line; and so inti- 

 mate is this connection that both might be 

 conveniently described together as a single 

 muscle. The fibres of the accelerator urinae 

 spring from the side of the raphe, and pass 

 from thence outwards and upwards upon the 

 urethra. The anterior fibres incline very ob- 

 liquely forwards and outwards to arrive at 

 the surface of the corpus cavernosum penis, 

 where they terminate. In consequence of this 

 disposition the acceleratores urinae muscles 

 are separated from each other in front by a 

 Y-shaped interval in which the urethra appears. 

 The succeeding fibres, after embracing the 

 urethra laterally, are lost on a short horizontal 

 tendon, which likewise receives the correspond- 

 ing fibres of the opposite muscle. This tendon 

 is placed above the urethra, beneath the junction 

 of the crura penis, and anterior to the triangular 

 ligament of the urethra. The posterior fibres 

 incline outwards more than the others, and are 

 inserted into the superficial surface of the 

 triangular ligament of the urethra, many of 

 them extending nearly to the cms penis. The 

 accelerator urinae muscle lies on the bulb and 

 the neighbouring portion of the corpus spongi- 

 osum. In conjunction with its fellow it con- 

 stitutes a fleshy sheath, all but perfect, for the 

 urethra. Its action is to compress the canal, 

 and at the same time to draw forwards the 

 bulb. It is employed in expelling the semen 

 and the last drops of urine from the sinus of 

 the bulb ; and by contracting spasmodically it 

 may even arrest the progress of a catheter, an 

 occurrence explained by the manner in which 

 many of its fibres completely surround the 

 passage. 



The erector penis muscle (called sometimes 

 " the compressor penis," or " the ischio-caver- 

 nosus,") is placed obliquely along the lateral 

 margin of the genito-urinary division of the 

 perineum, where it partially envelopes and 

 conceals from view the corresponding cms 



VOL. in. 



penis. It is elongated, broader in the centre 

 than at the extremities, and curved so as to 

 embrace the crus on which it is moulded. 

 The erector penis springs by a narrow tendi- 

 nous attachment from the inner surface of the 

 tuber ischii, and from the extremity of the great 

 sciatic ligament beneath the transversus perinei 

 muscle; the fleshy fibres soon succeed, and 

 after continuing in an oblique direction up- 

 wards, forwards, and inwards, they end in 

 a fibrous expansion which inclines outwards 

 and forwards to terminate by two processes on 

 the surface of the corpus cavernosum penis. 

 Anatomists are not agreed on the action of this 

 muscle: it may serve to draw down and to 

 compress the crus penis, and in that manner to 

 influence the circulation therein, but it can 

 have no direct concern in causing the erection 

 of the organ. 



The transversus perinei muscle (" the ischio- 

 perineal" of some anatomists) passes from the 

 tuber ischii to the central tendinous point of 

 the perineum ; in this course the muscle in- 

 clines forwards and slightly downwards, so that 

 its direction is not exactly transverse. It is 

 attached externally to the inside of the tuber 

 ischii, above the origin of the erector penis and 

 the crus penis; and internally it is confounded 

 with the several muscles already specified as 

 reaching the central tendinous point. The 

 transversus perinei is often of a triangular 

 shape, the base at the ischium, and the apex 

 at the central tendinous point of the perineum ; 

 it is mostly fleshy, except at its insertion, which 

 is aponeurotic. This muscle is exceedingly 

 uncertain as regards its developement, being 

 sometimes replaced by a few scattered fibres 

 derived apparently from the levator ani, and 

 occasionally reinforced by a second muscle, 

 termed the transversus perinei alter. The 

 transversus perinei alter, when present, lies 

 anterior and superior to the other, and extends 

 from the ramus of the ischium to the bulb, 

 where it becomes confounded with the accele- 

 rator urinse. The transversus perinei is related 

 by its superficial surface to the superficial peri- 

 neal fascia, the superficial perineal and the 

 transverse perineal vessels and nerves, the inser- 

 tion of the superficial sphincter ani, and the 

 origin of the erector penis and the crus penis. 

 Its deep relations are the levator ani and Wil- 

 son's muscles, together with the triangular 

 ligament of the urethra. The transversus peri- 

 nei contributes to the strength of the perineum 

 by raising and fixing the central tendinous 

 point ; it also assists the levator ani in raising 

 and supporting the rectum and the pelvic vis- 

 cera. The transversi perinei muscles have been 

 by some described as a single digastric muscle, 

 semilunar in shape, and with the concave mar- 

 gin directed backwards and upwards towards 

 the gut.; the result of the simultaneous action 

 of these two bellies would be to raise and 

 compiess the intestine in front, and thus to 

 assist in completing the process of defaecation. 



The triangular spaces are situated one at 

 either side of the urethral prominence; each is 

 bounded internally by the accelerator urinae 

 and the urethra, externally by the erector penis 



3 o 



