THE MUSCLES AND FASCLE OF THE ABDOMEN. 327 



THE MUSCLES AND FASCIJE OF THE ABDOMEN. 



FASCIAE. The superficial fascia of the abdomen is usually described as con- 

 sisting of two layers. One of these, the subcutaneous layer, corresponds in its 

 general features with the areolar subcutaneous tissue of other parts of the body, 

 and contains embedded in it a very variable and often large quantity of fat. The 

 other, or deeper layer, is of a denser and more membranous structure, and contains 

 a considerable amount of yellow elastic tissue in its substance ; it is only connected 

 by loose areolar tissue to the subjacent aponeurosis of the external oblique muscle, 

 except at the umbilicus and along the linea alba, where the attachment is more 

 intimate, while inferiorly a fibrous and elastic expansion of considerable strength, 

 derived from this layer, passes from the lower part of the linea alba and the sym- 

 physis pubis to the dorsum of the penis, constituting the suspensory ligament of 

 that organ. These two layers are both continuous with the superficial fascia on 

 other parts of the trunk : they can be dissected as distinct layers only on the fore 

 part of the abdomen, and they are separated in a more marked manner in the 

 immediate neighbourhood of the groin, where subcutaneous vessels, such as the 

 superficial epigastric and circumflex iliac, as well as lymphatic glands, lie between 

 them. This distinct portion of the deeper layer is known as the fascia of Scarpa, 

 and passing down freely over Poupart's ligament it ends immediately below that 

 band by becoming blended with the fascia lata ; but internally, near the external 

 abdominal ring, it remains free and is prolonged downwards over the spermatic cord 

 to the scrotum. The subcutaneous layer, losing its fat, is combined with the deeper 

 layer as they both pass to the scrotum ; and here the united layer acquires a reddish 

 brown colour, and undergoes a modification of structure by becoming mingled 

 largely with involuntary muscular fibres, constituting the dartos tunic of the scrotum. 

 Some involuntary muscular fibres also exist in the altered superficial fascia which 

 covers the penis. This covering, on leaving the scrotum posteriorly, becomes 

 continuous with the superficial fascia of the perineum. 



The parts of the superficial fascia here described have received minute attention from 

 anatomists, by reason of their close relation to the seat of hernial tumours and other patho- 

 logical conditions ; the adhesion of the fascia below Poupart's ligament, and its disposition 

 over the inguinal aperture, spermatic cord, and scrotum, while they prevent the descent upon 

 the thigh of fluid which has been effused beneath the fascia, cause it either to spread upwards 

 upon the abdomen or to take its course downwards into the scrotum. 



The deep layer of the abdominal fascia is also interesting as corresponding with the tunica 

 abdominalif of animals, a strong membrane consisting almost entirely of yellow elastic tissue, 

 which may be well seen in the horse or ox, and which contributes to the support of the 

 viscera. 



MUSCLES. The muscular wall of the abdomen is mainly formed on each side by 

 three layers of muscle, the fibres of which run in different directions, those of the 

 superficial and middle layers being oblique, and those of the innermost layer being 

 transverse. In front, these three layers of muscle are replaced by tendinous ex- 

 pansions, which meet in the middle line, giving rise to the linea alba : on each side 

 of this line the fibres of the rectus muscle extend in a vertical direction between 

 the tendinous layers, supported usually at the lower end by the pyramidalis muscle. 

 Posteriorly, the wall is formed in part by aponeurosis, and in part by muscles of 

 which the fibres are chiefly vertical, viz., the muscles of the back, and in front of 

 them the quadratus lumborum. 



The obliquus externus abdominis muscle, the strongest and most superficial 

 of the three broad muscles of the abdomen, arises from the outer surface of the 

 lower eight ribs, by slips arranged in a serrated series, four or five of them inter- 

 digitating with origins of the serratus magnus, and three or four with origins of the 



