PERINEUM. 841 



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 ischiatic tubero- 

 sity, 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 pubic nerve lying below the artery. Crossing the 

 space transversely, about its centre, are the inferior hasmorrhoidal 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 lithotomy, or of 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 tuberosi- 

 ties of the ischia. 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 extent of the base 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 near together, it would be necessary to make the incisions in the 

 lateral operation of lithotomy less oblique than if the tuberosities were widely 

 separated, and the perineal space, consequently, wider. The perineum is sub- 

 divided by the median raphe into two equal parts. Of these, the left is the one 

 in which the operation of lithotomy is performed. 



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 re- 

 moved 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 re- 

 moved, in the manner shown in Figs. 455, 6, the superficial fascia is exposed. 



The Superficial Fascia 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 con- 

 tinuous 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 mus- 

 cles 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 ischiurn, external to the crus penis, and as far back as the tuberosity 

 of the ischium; posteriorly, it curves down behind the Transversus Perinasi 

 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. 



In rupture of the anterior portion of the urethra, accompanied by extravasa- 

 tion of urine, the fluid makes its way forwards, beneath this fascia, into the 



