202 THE FASCIAE IN GENERAL. 



FASCLEJ. 



The term fascia is applied to parts presenting a membranous disposition of 

 reticulated or felted fibrous tissue. These structures are usually distinguished as the 

 superficial and the deep ; the former consisting of looser and finer material, and 

 passing by their slenderer kinds into the looser varieties of connective tissue ; while 

 the latter, denser in character, frequently exhibit more or less regular arrangements 

 of strong white fibres, giving them a shining appearance, and are often termed 

 aponeuroses. 



Superficial fascia. Under this name, or as subcutaneous fascia, is described 

 the layer of loose tissue of varying density, which is placed immediately beneath the 

 skin, all over the body. It is the web which contains the subcutaneous fat, the 

 panniculus adiposus, and in some regions superficial muscles, which constitute the 

 panniculus carnosus. From the subcutaneous tissue of the eyelids, however, as well 

 as from that of the penis and scrotum, adipose matter is entirely absent. Beneath 

 the fatty layer of the superficial fascia, which is immediately subcutaneous, there is 

 generally another layer of the same structure, comparatively devoid of adipose tissue, 

 in which the trunks of the subcutaneous vessels and nerves are found. When the 

 subcutaneous fat becomes absorbed, the stroma in which it was deposited is still left, 

 and its meshes approach one another, so that in lean subjects a more fibrous con- 

 dition of the superficial fascia is found than in others. 



Deep fasciae and aponeuroses. Under the name of deep fascia is compre- 

 hended that stronger layer of fibrous or connective tissue which, lying close to the 

 muscles, invests them, or dips between them, and forms a nearly continuous covering 

 of the body beneath the superficial fascia. It is chiefly to the stronger parts of this 

 fascia that the name of aponeuroses has been given. Those covering the muscles 

 have been named aponeuroses of investment, to distinguish them from proper ten- 

 dinous expansions, or aponeuroses of insertion, of muscles. This distinction, however, 

 is far from being universally applicable : aponeuroses of insertion are often continued 

 into aponeuroses of investment, as in the instance of the gluteus maximus, or into 

 softer fascia, as at the lateral parts of the occipito-frontal aponeurosis. The 

 principal aponeuroses of investment are those which encase the muscles of the limbs, 

 binding them down in a common sheath, and connected in various places either 

 directly or by septa with the bones. Parts of the deep fasciae in the vicinity of the 

 larger joints, as at the wrist and ankle, become strengthened into tight transverse 

 bands which serve to hold the tendons close to the bones, and hence receive the name 

 of retinacula or annular ligaments. 



Synovial sacs and sheaths : bursse mncosae. In various situations where 

 the tendons of muscles pass over the prominences of bones, or run in fibrous sheaths, 

 synovial cavities exist, either of a vesicular or tubular form, thus forming the synovial 

 bursce, or sheaths. In many such instances a true synovial membrane appears to cover 

 the adjacent surfaces, and diminishes their friction in moving on each other. In 

 other places less defined spaces exist in the connective tissue between parts of the 

 tendons or fasciae, and occasionally between parts of the skin and the harder or more 

 prominent structures on which they lie. In some of these subcutaneous bursse a 

 distinct synovial membrane cannot be found ; and there are probably gradations of 

 transition between these bursal spaces and those which are lined by syuovial mem- 

 brane. Some of the synovial sacs and sheaths of tendons in the vicinity of joints 

 communicate freely with the articular cavities. (See Gen. Anat., Vol. I.) 



