ANUS— RECTUM 



112< 



ment; (7) levator ani; (8) capsule of prostate. Furtlicr. these fasciie of the urethral 

 triangle (p. 1128) are so arranged as to form a superficial deep compartment, 

 and within one or other of these all the structures of this most inij.oriant (Hvisioii 

 of the perinteum are found. Thus the superficial compartment is hounded, in 

 front, hy the fascia of Colics; behind, by the triangular ligauient; laterally, Ijy 

 the attachment of these to the margins of the pubic arch; and, l)ehind. by the 

 blending of the fascia of Colles with the base of the triangular ligament. The c(tn- 

 tents of this compartment are given elsewhere. The deeper compartment is the 

 interval between the two layers of the triangular ligament. 



Ischio-rectal fossa. — Most of the Itoundaries of this space (p. 1063) can be 

 made out with the linger in a tiiin subject. The loose, j)Oorly vitalised fat which 

 occupies it, the dependent position of the i>art, its terminal blood-supply, its expo- 

 sure to cold and damp, and the close vicinity of decomposing ficces, all account for 

 the frequency of abscess here. The position of the pudic vessels and nerve in their 

 sheath of obturator fascia, on the outer wall, aV)0ut an inch and a half above the 

 lower margin of the tuber ischii, must be remem])ered. 



Fig. 696. 



-Section showixo the Isc.'hio rectal Fossa ix its Relations to the 

 Pelvic Visceea. 



Levator ani v^ith recto-vesioal 

 and iBchio-rectal fasciae 



Obturator internus 



I/ilenial pudic vessels and 

 XER VES in ob/iirnlor fusein 

 TUBER ISCHII 

 Ischio-rectal foasa with its 

 anterior and t>08terior ex- 

 tensions 



Gluteus mazimuB 



SYMPHVSIS PUBIS 



Pubo-proBtatic ligaments 

 Proxlatic plexus 



PROSTATE 



Capsule of prostate formed 



by recto-vesical fascia 

 Fat 



RECTUM INVESTED BY RECTO- 

 VESICAL FASCIA 



Anus. — The tightly closeel (condition of this oriliee in health and the puekering 

 of the skin around, due to the sphincter and corrugator cutis ani, are characteristic. 

 Dilated veins, external piles, or tags of skin resulting from the shrinking of these, 

 are also common. A white line, varying in distinctness in different subjects, 

 marks the junction of the skin, and mucous membrane, and the interval lietween 

 the external and internal sphincters .(Hilton). Amongst the numerous folds 

 about the anal orifice, a fissure or ulcer may be hidden, esjtecially on the coccygeal 

 aspect; the alumdant nerve-supply to this region and the large distribution of the 

 ])udic nerve to the genitals, and the junction of this nerve with other branches of 

 the sacral plexus, explain the acuteness of the suft'ering, and its wide distril)Ution 

 in these afifections (Hilton). 



Rectum. — The following points can be made out by the finger introduced here: 

 (1) The thickened, roll-like feel of a contracted external sphincter; (2) tlie narrower, 

 more expanded, internal sphincter extending upwards for an inch from this; (3) 

 the condition of the iseliio-rectal fossa? on either side; (4) the membranous urethra 

 in front, especially if a staff has been introduced; (5) just beyond the si)hincters, 

 or an inch and a half within the anus, lies the prostate: (6) converging towards 

 the base of the prostate, and forming the sides of the triangular space, are the vesi- 



