The superficial fascia of the abdomen has attracted the attention of anatomists and sur geons from its connexion with all herniary tumours in that region. In its arrangement it is much less complex than the cervical fascia, being a uniform membranous expansion spread over the superficial muscular and aponeurotic structures of the abomen, continuous on either side and posteriorly with the superficial fascia of the lumbar regions, and inferiorly with that of the inferior extremities. See the description of it in the article ABDOMEN.
The superficial fascia of the limbs is com pletely confounded with the subcutaneous cel lular tissue, and wants that condensation by which on the trunk generally, but particularly in the neck and abdomen, it is distinguished.
There can be no doubt that the superficial fascia is no more than condensed cellular mem brane, and its variety of appearance in different regions depends in a great measure upon pecu liarities in the motions and arrangement of the parts contained in those regions, e.g. wherever the muscles of a part are in very frequent ac tion, and at the same time the fascia is com pressed between the integument and the mus cles, it suffers condensation ; this is conspicuous in the abdomen, where there is almost incessant muscular action in consequence of the respi ratory movements, and where the weight of the viscera, thrown forwards in the erect posture, occasions a considerable pressure upon the an terior and lateral portions of the abdominal parietes. The deposition of adeps to any great extent is unfavourable to the existence of a distinct fascia superficialis, which is thereby, as it were, decomposed, and hence this fascia is not distinct from the subcutaneous cellular tissue in those regions where, either habitually or preternaturally, this substance is largely de posited.
The superficial fascia is identified with the subcutaneous cellular membrane in the cranial regions, a circumstance which seems attributa ble to the firm adhesion of the aponeurotic ex pansion of the occipito-frontalis muscle to the subcutaneous tissue, and also the cutaneous insertion of other muscles; to a similar cause we may ascribe the indistinctness of this fascia in the face also, as likewise to the great depo sition of fat in some parts of this region. In the pectoral region it is attenuated, and is more intimately connected with the proper cellular covering of the great muscles than with the subcutaneous cellular tissue.
Where the superficial fascia has suffered condensation to a considerable extent, and there is a complete absence of adipose sub stance, it assumes an appearance which has given rise to the designation " filiro-cellular," in consequence of the existence of thick, white, and opaque bundles intersecting the membrane in various directions; these bundles seem to be produced by the close application of the walls of the cells to each other, and the conse quent obliteration of their cavities. This, how ever, I believe is the nearest approach that the superficial fascia makes to fibrous membrane ; and I am strongly disposed to question the accuracy of Velpeau's assertion, that it is some times transformed into the yellow fibrous or into muscular tissue. The elastic abdominal ex pansion, described by Girard, is certainly not a conversion of the superficial fascia, but of the muscular aponeurosis.
Among the cellular fascia, Velpeaus de scribes a layer of cellular membrane, pretty uniform in its characters, and in some localities of great practical importance, and gives it the name fascia superfu•alis interact. It is in contact with the serous membranes of the prin cipal cavities in the body, with those of the abdomen, thorax, and pelvis in particular; in the former of which it has attracted most atten tion under the denomination of the fascia pro pria. This cellular layer lies between the serous membrane and the fibrous layer which lines the parietes of the cavities, as for instance the fascia transversalis in the abdomen ; and consequently in this last cavity, when any viscus is protruded, carrying a peritoneal sac before it, this cellular layer uniformly forms the immediate investment of the sac, and is there fore called fascia propria, a hernial covering which every practical surgeon well knows is often of considerable density and thickness, and to which indeed is attributable the so-called thickening of the sac itself.
2. Apuneuroses or aponeurotic fascia.—This appellation should be confined to those textures which are purely fibrous, and belong to either the white fibrous tissue or the yellow. In man, they belong entirely to the former class, but we see some interesting examples among the lower animals, where, while the same characters as to intimate texture are preserved, they assume a yellow colour, and exhibit most manifestly the property of elasticity.