The triangular ligament of the urethra (" the deep perineal fascia" of some anatomists, "the perineal ligament " of AI. Carcassone, " the middle perineal aponeurosis" of AI. Blandin) presents itself next for examination. To expose the superficial surface of this ligament it is only further necessary to detach the crura penis from the bones and to free the bulb from its connections, but to exhibit the deeper surface satisfactorily the dissection must be conducted from within the pelvis. The triangular liga ment of the urethra extends from the rami of the ischium and pubis at one side to the cor responding edges of bone on the other; its superficial surface, directed forwards and down wards, is in contact (so long as the parts remain in situ) with the crura penis, the bulb of the urethra, and the muscles already specified ; its posterior surface, directed upwaids and back wards, is related to the prostate gland, the membranous portion of the urethra, Wilson's muscles, and the levatores ani; its base, directed downwards and backwards towards the rectum, gives attachment to the deep process of the superficial perineal fascia, and presents a double curvature, being prolonged in the middle line into a peak, which adheres to the central tendinous point of the perineum ; its apex corresponds to the lower extremity of the sym physis pubis, and includes the sub-pubic liga ment between its laminm, whilst its lateral inar gins adhere firmly to the rami of the ischium and pubis, and are distinctly continuous with the obturator fascia on either side. The opening which affords a passage to the urethra is si tuated about half an inch or rather less above the base of this ligament, and nearly one inch beneath the symphysis pubis, whilst that which ttansmits the dorsal veins of the penis is placed immediately below the sub-pubic ligament. The triangular ligament possesses uncommon strength ; it serves to fix and to strengthen the urethra and to fill up the arch of the pubis, completing the walls of the pelvis where the bones are deficient, and thus supporting power fully the abdominal and pelvic viscem. It con stitutes a perfect partition between the super ficial and the deep structures in the perineum, dividing the genito-urinary portion of this re gion into two distinct compartments ; and it consists of two laminw inseparably united to each other in some places, not so in others, for Cowper's glands, the sub-pubic ligament, the arteries of the bulb, the internal pudic vessels in a part of their course, and the so cal led muscles of Gu thrie, are developed between its layers.
Cowper's glands may be displayed by the careful removal of the superficial layer of the triangular ligament ; they are two small greyish bodies, each resembling a pea in shape and di rnensions, and placed one on either side be hind and above the bulb, beneath the mem branous portion of the urethra, and between the. laminte of the triangular ligament. Their ducts,' which open into the urethra in front of the bulbo have been already described.
Guthrie's muscles, two in number, are situ ated (according to their discoverer) between the layers of the triangular lig-arnent; each of them, as described by him, arises narrow and tendi nous from the descending ramus of the pubis near its junction with the ischium, and becom ing fleshy it passes tranversely inwards, and soon divides into two fasciculi, of which one spreads out on the upper surface and the other on the lower surface of the membmnous portion of the urethm. In this manner the muscles
from opposite sides meet in a tendinous raphe on the middle line of the urethm both above and below, the superior mphe being prolonged front the prostate gland to the junction of the crura penis, and the inferior mphe extending from the prostate to the bulb. Viewed either from above or from below, these muscles are fan-shaped, appearing expanded at the urethra and contracted at their origin from the bone, and they are believed to have the power of compressing the urethra so as to close the canal. Notwithstanding the accurate descriptions of Mr. Guthrie, many excellent anatomists have failed to demonstrate the exact arrangement of fleshy fibres which he has remarked, but the majority incline to the opinion that the peculiar reddish material in question is of a muscular nature.
The arteries of the bulb (one at either side) spring from the internal pudic after those ves sels have arrived at the triangular ligament of the urethra, and whilst they are overla.pped by the crura penis. Interposed between the la minw, and situated about a quarter of an inch above the base of the triangular ligament, the artery of the bulb runs nearly transversely in wards, and near the urethra divides into two branches, of which one is small and destined for Cowper's gland, whilst the other is of large size and perforates the bulb to supply the corpus spongiosum urethrx. The arteries of the bulb are of considerable marrnitude parti cularly after puberty, so that they bleed pro fusely when wounded ; they retract between the layers of the triangular ligament when divided, and this added to the narrowness of the peri neum in front, and to the distance from the surface at which they are placed, renders it diffi cult for the surgeon to secure their cut extremi ties or otherwise to control their hemorrhage. The consequences of such an accident may prove speedily fatal ; extreme care must there fore be taken to protect these vessels from the knife dining lithotomy.
The artery of the bulb is endangered in the second period of the lateral operation whilst the surgeon cuts into the membranous portion of the urethra to lay bare the groove of the staff. The knife should be introduced into the urethra behind the bulb, and below and behind the course of the artery, and little or none of the triangular ligament except the posterior lamina where it invests the menibranous portion of the urethm, should be divided in this incision, for the %essel requiring protection lies about one quarter of an inch above the base of the liga ment, and therefore none but the very lowest fibres of that structure can be cut with impu nity ; in short the incision must be made into the membranous portion of the urethra as it lies behind the- triangular limament, and the bulb must be studiously avoided. Irregularities in the direction of these arteries calculated to em barrass the operating surgeon are occasionally encountered ; arising sometimes prematurely from the pudic, they ascend very obliquely to the bulb; and again, although given off from the pudic at the usual place, they now and then take a curved course to their destination, the convexity of the curvature looking downwards and backwards ; when either of these varieties occurs, the vessels in question run much closer to the base of the triangular ligament than usual, and are therefore imminently endangered in lithotomy.