In and between these several structures ramify the various arteries, veins, lymphatics, and nerves, which constitute the vascular and ner vous supply to the abdominal parietes.
1. The skin on the anterior and lateral parts of the abdomen is thin and smooth, and in some parts covered with hairs, as along the middle line, especially below the umbilicus and over the pubic region. Along the median line the cutaneous follicles are largely developed, and during pregnancy an increased secretion of pigmentum is said to take place, producing a brownish colour of the skin in these regions. In women who have borne children, the skin becomes wrinkled to a considerable de gree, and the epidermis exhibits, as Winslow has remarked, a great number of lozenge shaped spaces disposed in a reticular manner.* In the epigastric region the skin is much more sensitive during life than in the other parts of the abdomen, and with some persons sympathizes with the stomach in a remarkable degree, so that pressure on it even in the healthy state produces a degree of pain or un easiness in that organ, or even a tendency to nausea. In the umbilical region we observe a depression, the floor of which is more or less elevated in the centre. This depression is de nominated the navel or umbilicus, (the dimi nutive of umbo, a nob or button.) It is produced by the firm adhesion of the skin to the subjacent structures, its true nature being that of a cicatrix, occupying the site of a former perforation through which the umbilical arteries and veins and the urachus passed in maintaining the circulation between the foetus and placenta. In very fat persons, the depth of the depression is often very much increased by reason of the great thickness of the abdomi nal parietes, and in some instances its form assumes that of a slit, and sometimes, instead of a depression, there is a greater or Jess pro minence of the integument.
In the lumbar region the skin is thicker and firmer than in the others; and we generally find it in a state of congestion after death, in consequence of the position of the body.
2. The subcutaneous cellular' tissue on the anterior surface of the abdomen has obtained especial attention from anatomists, particularly that portion of it which is found in the hypo gastric regions. It is denominated the superficial
fascia,t and is merely an expanse of cellular tissue possessing the same general characters as that which is found in all other parts of the body ; it is continued upwards over the thorax, laterally into the region of the back, inferiorly along the thighs, and into the scrotum. It varies in thickness according to the quantity of fat which is deposited in its cells in some in stances it has been known to possess a thick ness of three inches. Thin but muscular subjects afford the best examples from which to study the superfical fascia of the abdomen : in such subjects we find it in general of a much denser character than in others, very strong and elastic and easily divisible into laminae, produced, no doubt, by the pressure which it experiences from the weight of the abdominal viscera, and the constant attrition occasioned by the action of the abdominal muscles. In the iliac region, immediately above Poupart's ligament, the density of this fascia is most conspicuous. Here some have regarded it as a fibro-cellular membrane ; but the opaque bands which give it a fibrous appearance are merely the walls of the membranous cells rendered thicker and denser than they are in other parts. I cannot agree with Beclardt that it presents almost all the characters of an aponeurosis, inasmuch as it differs from an aponeurosis in wanting the shining and regular surface, and in possessing a degree of elasticity which never belongs to aponeurotic expansions. The elasticity of the superficial fascia is remarkable, and is by some compared to the elastic expansion over the abdomen of the larger quadrupeds ;1 the comparison, however, is inaccurate, inasmuch as they are two distinct tissues, the former being cellular, and the latter the aponeurosis of the oblique muscles, which in some degree partakes of the properties of the yellow elastic fibrous tissue (tissu jaune).