The superficial perinea] fascia is a celiulo aponeurotic expansion interposed between the integuments and the principal muscles, &c. of the region, (to this, however, the superficial sphincter muscle, which is absolutely subcuta neous, forms an exception -) in the anterior or genito-urinary division of the perineum it is of very considerable thickness, being mostlycellu lar and fatty superficially, and becoming more dense the deeper the dissection is carried ; nu merous fibrous bands are interwoven with this expansion, and appear more and more evident the farther from the integument it is examined, so that at length, just like the superficial fascia of the abdomen, it assumes very much the cha racters of fibrous membrane. The varieties in density which this fascia presents in different subjects are nearly endless ; in corpulent per sons its grossness is sometimes excessive, and when condensed by inflamination its depth be comes extreme : this explains the surprising distance from the surface to which the surgeon usually cuts in liberating the matter of a peri neal abscess, and shews the lithotomist the ne cessity of duly estimating the thickness of this structure before he commences his operation. Traced forwards the superficial fascia becomes gradually thinner until at length it degenerates into cellular membrane continuous almost with out line of demarcation with the dartos, and as it approaches the scroturn it becomes loose in texture, whilst its cells communicate freely with each other and contain little adipose substance, if any. Followed laterally it seems at first sight to merge gradually into the subcutaneous cellular tissue of the thigh, but when examined from beneath by being mised in a flap from the rniddle line outwards, it is found to adhere by strong tendinous attachments to the edge of the pelvis, and so powerful is this adhesion that all attempts to pass the handle of a scalpel out wards between the fascia and the rami of the pubis and ischium uniformly fail, In the posterior or anal division of the peri neum the superficial fascia is little more than a cellular web, appearing, however, somewhat denser in the space between the tuber ischii and the anus; here its continuity with the subcutaneous cellular rnembrane of the gluteal region may be easily demonstrated, and it also dips in deeply into the ischio-rectal fossa, where its cells become inordinately loaded with fat. If the superficial fascia be carefully raised from before backwards, a deep process of this membmne may be seen to form a partiticn between the genito-urinary and the anal divi sions of the perineum. The process referred to constitutes a septum, which, after dipping in deeply behind the transversi perinei muscles, becomes identified with the base of the trian gular ligarnent of the urethra; to demonstrate this connection, however, requires some nicety of manipulation and a suitable subject. In raising this fascia the anatomist cannot fail to observe that its adhesion to the subjacent parts is everywhere extremely loose, except it' the situations already specified.
The peculiar structure and the connections of the superficial perineal fascia afFord a satisfac tory explanation of the course which urinary effusions generally take in the living subject. When urine escapes into the perineum in con sequence of rupture or ulcemtion of the ure thra, provided the solution of continuity be seated superficial to the triangular ligament of the urethra, the liquid makes its way forwards to the scrotum, and after distending that part it proceeds upwards to the abdominal parietes, occasionally reaching the umbilicus, or even attaining to a higher level. The effusion rarely passes downwards along the thighs, or back wards to the neighbourhood of the anus, and its progress to the surface in the perineum is invariably tedious. In such cases the close
adhesion of the superfieial fascia to the mmi of the pubis and ischium prevents the urine from reaching the thigh ; the connection of the superficial fascia to the base of the triangular ligament of the urethra opposes its progress towards the anus; the density of the triangular ligament of the urethra impedes its passage into the pelvis; whilst the loose connection between the superficial fascia and the subjacent structures in front, the remarkable laxity of the dartos, and the continuity of this latter with the superficial fascia of the perineum on the one hand, and with that of the abdomen on the other, are so many circumstances inviting, the stream to the scrotum, the penis, and the walls of the abdomen. The promptest treat ment is demanded to remedy mischief such as has been described. A free division of the integuments and fascia in the perineum over the seat of rupture, for the purpose of giving the urine vent and putting a stop to further effusion, becomes indispPnsable, and without this measure all others must be unavailing.
The laxity of the superficial fascia as it approaches the scrotum should deter the sur geon from commencing his cutaneous incisions in the lateral operation of lithotoiny too far forwards, lest urinary infiltration should ensue; and the density of the same structure in other situations indicates an early incision for the release of matter imprisoned beneath it.
For a description of the posterior or anal division of the perineum, including the ischio rectal fossm and the neighbouring fibrous mem branes, the reader is now referred to the arti cle ANus, where all the structures connected with the lower extremity of the rectum are described in detail. It should be borne in mind, however, that some branches of arteries (the inferior or external hemorrhoidal) pass across the ischio-rectal fossw, entangled in the fat which occupies those excavations. The inferior hemorrhoidal vessels are usually three in number at each side; they derive their origin from the internal pudic artery, as it lies be neath the obturator fascia; their destination is the lower extremity of the gut and its appen dages, and one of them (the most anterior) gains the front of the intestine to anastomose with a similar vessel from the opposite side, and with branches of the transversalis perinei also. The inferior hemorrhoidal vessels are rernarkably tortuous and rather uncertain in their course ; the anterior of them is sometimes divided in the lateral or bilateral operations of lithotomy, a circumstance which has led to this cursory notice of their anatomy.
When the superficial fascia has been dis placed, many new parts become apparent in the genito-urinary division of the perineum ; a quantity of loose adeps and also a very thin glistening fibrous expansion which adheres closely to the subjacent muscles and obscures the dissection, must, however, be carefully re moved before the deeper structures are satis factorily displayed. The central tendinous point of the perineum, the superficial perineal bloodvessels and nerves, the transversalis peri nei artery with its accompanying veins and nerves at each side respectively, the urethra itself, still however obscured by the accelera tores urinm muscles, the crura penis, each partly enveloped by the erector penis nauscle, the transversi perinei muscles, and two small trian gular spaces bounded by muscles and placed one at either side of the urethral prominence, arc the principal objects which come into view.