378 MYOLOGY 



Fat is entirely absent in the subcutaneous tissue of the eyelids, of the penis 

 and scrotum, and of the labia minora. It varies in thickness in different parts of 

 the body; in the groin it is so thick that it may be subdivided into several laminae. 

 Beneath the fatty layer there is generally another layer of superficial fascia, com- 

 paratively devoid of adipose tissue, in which the trunks of the subcutaneous vessels 

 and nerves are found, as the superficial epigastric vessels in the abdominal region, 

 the superficial veins in the forearm, the saphenous veins in the leg and thigh, and the 

 superficial lymph glands. Certain cutaneous muscles also are situated in the super- 

 ficial fascia, as the Platysma in the neck, and the Orbicularisoculi around the eyelids. 

 This fascia is most distinct at the lower part of the abdomen, perineum, and extremi- 

 ties; it is very thin in those regions where muscular fibers are inserted into the 

 integument, as on the side of the neck, the face, and around the margin of the anus. 

 It is very dense in the scalp, in the palms of the hands, and soles of the feet, forming a 

 fibro-fatty layer, which binds the integument firmly to the underlying structures. 



The superficial fascia connects the skin to the subjacent parts, facilitates the 

 movement of the skin, serves as a soft nidus for the passage of vessels and nerves 

 to the integument, and retains the warmth of the body, since the fat contained in 

 its areolae is a bad conductor of heat. 



The deep fascia is a dense, inelastic, fibrous membrane, forming sheaths for the 

 muscles, and in some cases affording them broad surfaces for attachment. It 

 consists of shining tendinous fibers, placed parallel with one another, and connected 

 together by other fibers disposed in a rectilinear manner. It forms a strong invest- 

 ment which not only binds down collectively the muscles in each region, but gives a 

 separate sheath to each, as well as to the vessels and nerves. The fasciae are thick 

 in unprotected situations, as on the lateral side of a limb, and thinner on the medial 

 side. The deep fasciae assist the muscles in their actions, by the degree of tension 

 and pressure they make upon their surfaces; the degree of tension and pressure 

 is regulated by the associated muscles, as, for instance, by the Tensor fasciae latae 

 and Glutaeus maximus in the thigh, by the Biceps in the upper and lower extremi- 

 ties, and Palmaris longus in the hand. In the limbs, the fasciae not only invest 

 the entire limb, but give off septa which separate the various muscles, and are 

 attached to the periosteum : these prolongations of fasciae are usually spoken of as 

 intermuscular septa. 



The Fasciae and Muscles may be arranged, according to the general division 

 of the body, into those of the head and neck; of the trunk; of the upper extremity; 

 and of the lower extremity. 



THE FASCLffi AND MUSCLES OF THE HEAD. 



I. THE MUSCLE OF THE SCALP. 



Epicranius. 



The Skin of the Scalp. This is thicker than in any other part of the body. It is intimately 

 adherent to the superficial fascia, which attaches it firmly to the underlying aponeurosis and 

 muscle. Movements of the muscle move the skin. The hair follicles are very closely set together, 

 and extend throughout the whole thickness of the skin. It also contains a number of sebaceous 

 glands. 



The superficial fascia in the cranial region is a firm, dense, fibro-fatty layer, 

 intimately adherent to the integument, and to the Epicranius and its tendinous 

 aponeurosis; it is continuous, behind, with the superficial fascia at the back of the 

 neck; and, laterally, is continued over the temporal fascia. It contains between 

 its layers the superficial vessels and nerves and much granular fat. 



The Epicranius (Occipitofrontalis) (Fig. 378) is a broad, musculofibrous layer, 



