Inferiorly the superficial fascia moves freely over Poupart's ligament, and is continued over the thigh (see GROIN, REGION OF THE). Along the middle line it is very adherent to the sub jacent aponeurotic structure (the linea alba) as well as to the skin,—a fact which may be remarked of the subcutaneous cellular tissue in other parts of the body, and which was long ago noticed by Bordeu, when he observed that the cellular tissue is constricted (etranglee) in all its median portion, and that its cells ( ballons ou pouches) are closed over the axis of the body. When this superficial fascia is dissected off, a very thin layer of cellular membrane, perfectly diaphanous, is found to adhere to the subjacent aponeurotic expansion. *This will be found particularly adherent over Poupart's ligament, and is that which is referred to by some ana tomists (as Manec, Cloquet, &c.,) as a deep process of the superficial fascia which adheres to Poupart's ligament, and so forms a super-. ficial septum between the abdomen and thigh. To see this layer the superficial lamina should be raised by commencing the dissection of it below and carrying it upwards ; the expansion will then appear to arise from Poupart's liga ment, and spread over the subjacent aponeuro sis. In some subjects it is so thin as to appear to be little more than the proper cellular cover ing of the muscle and its aponeurosis, but in others it assumes a considerable degree of density. It may be called the deep layer of the superficial fascia ; it deserves attention from the fact that the femoral hernia, in its ascent on the abdomen, lies between it and the super ficial layer. It is to this fascia that Scarpa must allude under the name of " aponeurotic web of the muscle of the fascia lata," and hence some have called it Scarpa's fascia.* The whole of the superficial fascia has been called Camper's fascia, because it was first fully described by that writer.f On the posterior wall of the abdomen, in the lumbar regions, the cellular tissue is more abundant and more lax; here we frequently find it infiltrated with serous fluid, in conse quence of the usual supine posture of the body after death. It is continuous above with the subcutaneous tissue in the dorsal region, and below with that in the gluteal regions. It, too, is firmly adherent along the middle line to the lumbar spine anteriorly, and to the skin posteriorly.
3. Muscles and aponeuroses.—The abdo minal parietes owe their thickness chiefly to the muscular lamellae and the aponeurotic ex pansions, which enter into their composition. In the anterior and lateral walls we find on each side five pairs of muscles, of which four are constantly present. These are, 1, M. obli quus externus; 2, obliquus internus; 3, trans versalis ; rectus abdominis ; 5, pyramidalis, which last is frequently absent.
1. Obliquui externus. ( Obliguus descen dens ; costo-abdominal ; ilio-pubi-costo-abdoL mind.) When the superficial fascia covering the an terior and lateral surfaces of the abdomen has been dissected away, this muscle is brought into view. It consists of a flat muscular portion, situated superiorly and posteriorly, and of a tendinous or aponeurotic lamella anteriorly and inferiorly, but which is largest and strongest in the latter situation.
The muscular portion of the external oblique is attached by separate fasciculi to the external surfaces of the eight inferior ribs, from the fifth to the twelfth inclusive. These fasciculi indigitate at their attachment with similar ones, of the serratus magnus, from the fifth to the ninth inclusive, and of the latissimus dorsi from the tenth to the twelfth. From these points of attachment, described by most English anatomists as the origin of the muscle, the fibres pass obliquely downwards and forwards, with different degrees of ob liquity, the middle fibres being the most ob lique, the superior taking a direction nearly horizontally inwards, and the posterior ones passing nearly vertically downwards. The an terior and middle fibres are inserted into the outer convex border of the aponeurotic lamella of the muscle, but the posterior are inserted into the outer lip of the two anterior thirds of the crista of the ilium by short tendinous fibres.
The fibres of this muscle vary considerably in length, those which are highest up being the shortest, the middle ones the longest, and next in length the posterior fibres. The aponeurotic lamella of the external oblique muscle is found on the anterior part of the abdomen, both su periorly and inferiorly. In the former situa tion the aponeurosis is extremely thin and weak ; it is transparent, so that the upper extremity of the rectus muscle which it covers is visible through it. This, too, is the narrow est portion of the aponeurosis, which increases in breadth, strength, and thickness as it de scends. The aponeurosis, like the muscular portion, consists of a series of fibres, for the most part inclined obliquely downwards and inwards, excepting the superior ones, whose direction is horizontal. At several places these fibres are separated from each other so as to allow the subjacent muscle to be seen through the interval. At various parts the tendon is perforated by vascular apertures, which are oc casionally so enlarged as to admit little peri toneal prolongations to pass through them. Along the middle line, from the ensiform car= tilage to the symphysis pubis, the aponeurosis forms an interlacement with its fellow of the opposite side, and this interlacement with that of the subjacent' aponeuroses constitutes the tendinous line called linea alba, which, as Velpeau observes, may be regarded as the centre in which all the fibrous elements of the abdomen terminate. Just above the symphysis pubis, the decussating fibres are not inter mixed in the same manner as in other parts of the linea alba : there the bundle of one side crosses anteriorly or posteriorly to that of the other, without any union of fibres, to be in serted into the pubis of the side opposite to that from which it came.
A little above and external to the pubis, a separation of the fibres of the tendon of the obliquus externus takes place, leaving an opening which is denominated the external abdominal ring, through which the rounded bundle composed of the spermatic vessels and duct (the spermatic cord) passes in the male, and the round ligament of the uterus in the female. The aponeurotic fibres which form the immediate boundaries of this opening are termed the pillars of the ring, of which one is superior, internal, and anterior, the other is in ferior, external, and posterior, and passes behind the cord. External and inferior to this opening, we observe that the aponeurosis of the external oblique muscle is extended from the pubis to the anterior superior spine of the ilium. On the pubic side, the fibres, which are the same that form the inferior pillar of the ring, are in serted into the spine of the pubis, and being reflected backwards, outwards, and a little upwards, they are likewise inserted into the linea ilio-pectinea, which commences at the spine of the pubis. The lower margin of the tendon is thus folded back a little as it arches over the excavation between the pubis and ilium, so as to present towards the abdomen a slight channel-like excavation, which affords origin to the muscular fibres of the internal oblique as well as to those of the transver salis, whilst it has the appearance of a rounded ligamentous cord towards the thigh. In this manner is formed Poupart's ligament, which, contrary to what its usual name denotes, is not a distinct ligamentous cord, but the in ferior margin of the external, oblique stretched from pubis to ilium, and folded a little upon itself. By its superior margin it is continuous with the fibres of the tendon of the external oblique, which fall obliquely upon it by its in ferior margin it is intimately connected with the fascia lata of the thigh ; externally it is inserted into the anterior superior spine of the ilium; and by its pubic extremity it has three attachments, 1. to the body of the pubis ; 2. to the spine of the same; and 3. to the linea ilio-pectinea, constituting what has been called Gimbernat's ligament, which has a sharp slightly crescentic margin directed backwards and outwards to wards the femoral vessels.* (See GROIN,