224 MUSCLES OF THE PERINEUM. 



upper fasciculus of the transverse portion of the muscle ; so that it is 

 not a distinct muscle surrounding the membranous portion of the 

 urethra, and supporting it as in a sling, as described by Mr. Wilson, 

 but merely an upper origin of the transverse muscle. 



The compressor urethrae may be considered either as two symme- 

 trical muscles meeting at the raphe, or as a single muscle : I have 

 adopted the latter course in the above description, as appearing to me 

 the more consistent with the general connections of the muscle, and 

 with its actions. 



The TRANSVERSUS PERINEI arises from the tuberosity of the ischium 

 on each side, and is inserted into the central tendinous point of the 

 perineum.* 



Relations. By its superficial surface with the superficial perineal 

 fascia, and superficial perineal artery. By its deep surface with the 

 deep perineal fascia, and internal pudic artery and veins. By its pos- 

 terior border it is in relation with that portion of the superficial peri- 

 neal fascia which passes back to become continuous with the deep 

 fascia. 



To dissect the compressor urethrce, the whole of the preceding 

 muscles should be removed, so as to render the glistening surface of the 

 deep perineal fascia quite apparent. The anterior layer of this fascia 

 should then be carefully dissected away, and the corpus spongiosum 

 penis divided through its middle, separated from the corpus caver- 

 nosum, and drawn forwards, to put the membranous portion of the 

 urethra, upon which the muscle is spread out, on the stretch. The 

 muscle is, however, better seen in a dissection made from within the 

 pelvis, after having turned down the bladder from its attachment to 

 the os pubis, and removed a plexus of veins and the posterior layer of 

 the deep perineal fascia. 



The SPHINCTER ANI is a thin and elliptical plane of muscle closely 

 adherent to the integument, and surrounding the opening of the anus. 

 It arises posteriorly in the superficial fascia around the coccyx, and by 

 a fibrous raphe from the apex of that bone ; and is inserted anteriorly 

 into the tendinous centre of the perineum, and into the raphe of the 

 integument, nearly as far forwards as the commencement of the 

 scrotum. 



Relations. By its superficial surface with the integument. By its 

 deep surface with the internal sphincter, the levator ani, the cellular 

 tissue and fat in the ischio-rectal fossa, and in front with the superfi- 

 cial perineal fascia. 



The SPHINCTER ANI INTERNUS is a muscular ring embracing the 

 extremity of the intestine, and formed by an aggregation of the cir- 

 cular muscular fibres of the rectum. 



* I have twice dissected a perineum in which the transversus perinei was of 

 large size, and spread out as it approached the middle line so as to become fan- 

 shaped. The posterior fibres were continuous with those of the muscle of the 

 opposite side ; but the anterior were prolonged forwards upon the bulb and 

 corpus spongiosum of the urethra as far as the middle of the penis, forming a 

 broad layer which usurped the place and office of the accelerator urinae. 



