

ISCHIO-RECTAL FOSSA PERINEUM. 777 



ligament. This space is filled with a large mass of adipose substance, which 

 explains the frequency with which abscesses in the neighborhood of the rectum 

 burrow to a considerable depth. 



If the subject has been injected, on placing the finger on the outer wall of this 

 fossa, the internal pudic artery, with its accompanying veins and nerve, will be 

 felt about an inch and a half above the margin of the ischial tuberosity, but 

 approaching nearer the surface as they pass forwards along the inner margin of the 

 pubic arch. These structures are inclosed in a sheath formed by the obturator 

 fascia, the pudic nerve lying below the artery. Crossing the space transversely, 

 about its centre, are the inferior hemorrhoidal vessels and nerves, branches of the 

 pudic ; they are distributed to the integument of the anus, and to the muscles of 

 the lower end of the rectum. These vessels are occasionally of large size, and 

 may give rise to troublesome hemorrhage, when divided in the operation of litho- 

 tomy, or for fistula in ano. At the back part of this space may be seen a branch 

 of the fourth sacral nerve ; and, at the fore part of the space, a cutaneous branch 

 of the perineal nerve. 



PERINEUM. 



The Perineal Space' is of a triangular form ; its deep boundaries are limited, 

 laterally, by the rami of the pubes and ischia, meeting in front at the pubic arch ; 

 behind, by an imaginary transverse line, extending between the tuberosity of the 

 ischium on either side. The lateral boundaries vary, in the adult, from three 

 inches to three inches and a half in length, and the base from two to three inches 

 and a half in breadth ; the average diameter being two inches and three-quarters. 

 The variations in the diameter of this space are of extreme interest in connection 

 with the operation of lithotomy, and the extraction of a stone from the cavity of 

 the bladder. In those cases where the tuberosities of the ischia are approximated, 

 it would be necessary to make the incisions in the lateral operation of lithotomy 

 much less oblique, than if the tuberosities were widely separated, and the perineal 

 space, consequently, wider. The perineum is subdivided by the median raphe 

 into two equal parts. Of these, the left is the one usually selected to commence 

 the primary incisions in the operation of lithotomy. 



In the middle line, the perineum is convex, and corresponds to the bulb of the 

 urethra. The skin covering it is of a dark color, thin, freely movable upon the 

 subjacent parts, and covered with sharp crisp hairs, which should be removed 

 before the dissection of the part is commenced. In front of the anus, a prominent 

 line commences, the raphe, continuous in front with the raphe of the scrotum. 

 The flaps of integument corresponding to this space having been removed, in the 

 manner shown in figs. 388 391, the superficial fascia is exposed. 



The Superficial Fascia consists of two layers, as in other regions of the body, 

 superficial and deep. 



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 

 carefully removed, after it has been examined, when the deep layer will be 

 exposed. 



The deep layer of superficial fascia (superficial perineal fascia) is thin, aponeu- 

 rotic 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 pubes and 

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

 ischium ; posteriorly, it curves down behind the Transversus perinei 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 



