I9I6 



HUMAN ANATOMY. 



ischial tuberosities and rami, and the pubic rami laterally (Fig. 1627). It is divided 

 into two lateral symmetrical halves by a dense cutaneous ridge, the raphe, across 

 which, as it represents the junction of the two foetal halves of the perineum, no blood- 

 vessels pass from one side to the other ; and into two unsymmetrical antero- posterior 

 triangular portions by an imaginary transverse line drawn between the anterior 

 borders of the ischial tuberosities and running in front of the anus. The posterior 

 of these two divisions — the portion of the outlet of the pelvis which contains the 

 rectum and anus — is the rectal triangle (anal perineum). Its practical relations have 

 been sufhciently dealt with in the article on the rectum and anus (page 1693). 



The anterior division, the uro-genital tria7igle (urethral perineum), has for its 

 deep boundaries : posteriorly the deep layer of the superficial fascia (fascia of Colles) 

 as it passes behind the transverse perineal muscles to become continuous with the 

 inferior layer of the triangular ligament (page 563); laterally the rami of the pubes 



Internal per- 

 ineal nerve 



Inferior 

 pudendal 

 nerve 



Int. pudic artery 



Pudic nerve 



Anal fascia 



Inferior hemor-f 



rhoidal artery\ 



Inferior hemor 



rhoidal nerv 



or-| 



Position of 

 urethra 



Colles's fascia 



Sphincter ani 

 extenius 

 Tuber ischii 



Tip of coccyx 



Dissection of perineum, showing superficial and hemorrhoidal branches of internal pudic 

 artery and of pudic nerves on right side ; Colles's fascia exposed on left. 



and ischia ; anteriorly the pubic arch. Over the uro-genital triangle the superficial 

 fascia is separable into two distinct layers, the superficial and the deep. The super- 

 ficial layer contains a considerable amount of fat, and is continuous with the corre- 

 sponding layer over the thighs and buttocks and with the masses of fatty tissue that 

 fill the ischio-rectal fossae. The deep layer, or fascia of Colles, is membranous and 

 free from fat, and is not only applied closely to the lower edges of the transverse 

 perineal muscles and attached to the base of the inferior layer of the triangular liga- 

 ment, but is also attached to the external margin of the rami of the pubis and ischium. 

 Anteriorly it is continuous with the deep layer of superficial fascia of the scrotum 

 (dartos), penis, and spermatic cords, and with the fascia of Scarpa (page 515) 

 on the front of the abdomen. When it is divided, a definite space, the siiperjicial 

 perineal interspace , is opened, which is bounded below by Colles's fascia, above by 

 the inferior layer of the triangular ligament, laterally by the attachments of the fascia 



