782 SURGICAL ANATOMY OF THE PERINEUM. 



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 ; posteriorly, 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 sphincter and Transversus perinei 

 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 with 

 the prostate gland, descending by its side and surrounding it as in a sling, it has 

 been described by Santorini and others as a distinct muscle, under the name of 

 the Levator prostatae. In the female, the anterior fibres of the Levator ani descend 

 upon the sides of the vagina. 



Relotiont. By its upper or pelvic surface with the recto-vesical fascia, which 

 separates it from the viscera of the pelvis and from the peritoneum. By its outer 

 or perinea! surface, it forms the inner boundary of the ischio-rectal fossa ; is 

 covered by a quantity of fat, and by a thin layer of fascia continued from* the 

 obturator fascia. Its posterior border is continuous with the Coccygeus muscle. 

 Its anterior border is separated from the muscle of the opposite side by a triangular 

 space, through which the urethra, and, in the female, the vagina passes from the 

 pelvis. 



Actions. This muscle supports the lower end of the rectum and vagina, and 

 also the bladder during the efforts of expulsion. 



The Coccygeus is situated behind and parallel with the preceding. It is a 

 triangular plane of muscular and tendinous fibres, arising, by its apex, from the 

 spine of the ischium and lesser sacro-sciatic ligament, and is inserted, by its base, 

 into the margin of the coccyx and into the side of the lower piece of the sacrum. 

 This muscle is continuous with the posterior border of the Levator ani, and closes 

 in the back part of the outlet of the pelvis. 



Relations. By its inner or pelvic surface, with the rectum. By its external 

 surface, with the lesser sacro-sciatic ligament. By its posterior border, with the 

 Pyriforrnis. 



Action. The Coccygei muscles raise and support the coccyx after it has been 

 pressed backwards during defecation or parturition. 



Position of the Viscera at the Outlet of the Pelvis. Divide the central tendinous point of the 

 perineum, and separate the rectum from its connections by dividing the fibres of the Levator ani, 

 which descend upon the sides of the prostate gland, turn it backwards towards the coccyx, when 

 the under surface of the prostate gland, the neck and base of the bladder, the vesiculas seminales, 

 and vasa deferentia will be exposed. 



The Prostate Gland is placed immediately in front of the neck of the bladder, 

 around the prostatic portion of the urethra, its base being turned backwards, and 

 its under surface towards the rectum. It is retained in its position by the Levator 

 prostatse and by the pubo-prostatic ligaments, and is invested by a dense fibrous 

 covering, continued from the posterior layer of the deep perineal fascia. The 

 longest diameters of this gland are in the antero-posterior direction, and trans- 

 versely at its base ; and hence the greatest extent of incision that can be made 

 in it, without dividing its substance completely across, is obliquely outwards and 

 backwards. This is the direction in which the incision is made through it in 

 the operation of lithotomy, the extent of which should seldom exceed an inch in 

 length. The relations of the prostate to the rectum should be noticed : by means 



