238 MUSCLES AND FASCIAE. 



very liable to serous infiltration. The superficial fascia varies in thickness in 

 different parts of the body : in the groin it is so thick as to be capable of being 

 subdivided into several laminae, but in the palm of the hand it' is of extreme 

 thinness, and intimately adherent to the integument. The superficial fascia is 

 capable of separation into two or more layers, between which are found the 

 superficial vessels and nerves, and superficial lymphatic glands ; as the superficial 

 epigastric vessels in the abdominal region, the radial and ulnar veins in the fore- 

 arm, the saphenous veins in the leg and thigh, and, in certain situations, cutaneous 

 muscles, as the Platysma myoides in the neck, Orbicularis palpebrarum around 

 the eyelids. It is most distinct at the lower part of the abdomen,' the scrotum, 

 perineum, and in the extremities ; is very thin in those regions where muscular 

 fibres are inserted into the integument, as on the side of the neck, the face, and 

 around the margin of the anus, and almost entirely wanting in the palms of the 

 hands and soles of the feet, where the integument is adherent to the subjacent 

 aponeurosis. The superficial fascia connects the skin to the subjacent parts, serves 

 as a soft nidus for the passage of vessels and nerves to the integument, and retains 

 the warmth of the body, from the adipose tissue contained in its areolae being a 

 bad conductor of caloric. 



The aponeurotic or deep fascia is a dense, inelastic and unyielding fibrous 

 membrane, forming sheaths for the muscles, and affording them broad surfaces for 

 attachment ; it consists of shining tendinous fibres, placed parallel with one another, 

 and connected together by other fibres disposed in a reticular manner. It is 

 usually exposed on the removal of the superficial fascia, forming 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 outer side of a limb, and thinner on 

 the inner side. Aponeurotic fasciae are divided into two classes, aponeuroses of 

 insertion, and aponeuroses of investment. 



The aponeuroses of insertion serve for the insertion of muscles. Some of these 

 are formed by the expansion of a tendon into an aponeurosis, as, for instance, the 

 tendon of the Sartorius ; others do not originate in tendons, as the aponeuroses 

 of the abdominal muscles. 



The aponeuroses of investment form a sheath for the entire limb, as well as for 

 each individual muscle. Many aponeuroses, however, serve both for investment 

 and insertion. Thus, the aponeurosis given off from the tendon of the Biceps 

 brachialis near its insertion is continuous with, and partly forms, the investing 

 fascia of the forearm, and gives origin to the muscles in this region. The deep 

 fasciae assist the muscles in their action, by the degree of tension and pressure they 

 make upon their surface ; and, in certain situations, this is increased and regulated 

 by muscular action, as, for instance, by the Tensor vaginae fernoris and Gluteus 

 maximus in the thigh, by the Biceps in the leg, 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 beneath to the periosteum ; these 

 prolongations of fasciae are usually spoken of as intermuscular septa. 



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

 the body, into, 1. Those of the head, face, and neck. 2. Those of the trunk. 

 3. Those of the upper extremity. 4. Those of the lower extremity. 



MUSCLES AND FASCIAE OF THE HEAD AND FACE. 



The Muscles of the Head and Face consist of ten groups, arranged according 

 to the region in which they are situated. 



1. Epicranial Eegion. 6. Superior maxillary Eegion. 



2. Auricular Region. 7. Inferior maxillary Eegion. 



3. Palpebral Eegion. 8. Intermaxillary Eegion. 



4. Orbital Eegion. 9. Temporo-maxillary Eegion. 



5. Nasal Eegion. 10. Pterygo-maxillary Eegion. 



