460 THE MUSCLES AND FASCIA 



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 perinaei muscles at the 

 central tendinous point of the perinaeum. 



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

 connective 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 Levator prostates. In the female, the anterior fibres of the Levator ani descend 

 upon the side of the vagina. 



Relations. By its inner 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 perineal surface, it forms the inner boundary of the ischio-rectal fossa, and is 

 covered by a thin layer of fascia, the ischio-rectal or anal fascia, given off 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. 



Nerve-supply. A branch from the anterior division of the fourth sacral nerve. 



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

 also the bladder during the efforts of expulsion. It elevates and inverts the lower 

 end of the rectum after it has been protruded and everted during the expulsion of 

 the faeces. It is also a muscle of forced expiration. 



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

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

 spine of the ischium and lesser sacro-sciatic ligament, and 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 

 Pyriformis. 



Nerve-supply. A branch from the fourth and fifth sacral nerves. 



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

 pressed backward during defecation or parturition. 



Superficial Fascia. The superficial fascia of the perinaeum consists of two 

 layers, superficial and deep, as in other regions of the body. 



The superficial layer is thick, loose, areolar in texture, and contains much 

 adipose tissue in its meshes, the amount of which varies in different subjects. In 

 front, it is continuous with the dartos of the scrotum ; behind, it is continuous 

 with the subcutaneous areolar tissue surrounding the anus ; and, on either side, 

 with the same fascia on the inner side of the thighs. This layer should be care- 

 fully removed after it has been examined, when the deep layer will be exposed. 



The deep layer of superficial fascia (Fascia of Colles) is thin, aponeurotic in 

 structure, and of considerable strength, serving to bind down the muscles of the 

 root of the penis. It is continuous, in front, with the dartos of the scrotum ; on 

 either side it is firmly attached to the margins of the rami of the os pubis arid 

 ischium, external to the crus penis, and as far back as the tuberosity of the isch- 

 ium ; posteriorly, it curves down behind the Transversus perinaei muscles to join 

 the lower margin of the deep perineal fascia. This fascia not only covers the 

 muscles in this region, but sends down a vertical septum from its under surface, which 

 separates the back part of the subjacent space into two, being incomplete in front. 



The Central Tendinous Point of the Perinseum. This is a fibrous point in the 

 middle line of the perinaeum, between the urethra and the rectum, being about 

 half an inch in front of the anus. At this point four muscles converge and are 

 attached : viz. the External sphincter ani, the Accelerator urinae, and the two 



