492 



HUMAN ANATOMY; 



The Mastoid Region. — For the same reasons the practical anatomy of the soft 

 parts covering the remaining region of the skull — the mastoid — will be taken up 

 later (page 150S). 



The Face. — The skin of the forehead and cheeks is thin and vascular and the 

 cellular tissue beneath is loose. Therefore wounds bleed freely but unite rapidly ; 

 sloughing is rare ; cellulitis tends to spread ; oedema is common ; superficial infections 

 (favored by the constant exposure of the region J are attended by much redness and 

 swelling and little pain ; if they result in abscess, it is not apt to attain a large size, 

 as the delicacy of the skin permits of early pointing. On the other hand, necrotic 

 processes (as in cancrum oris) once established in the loose cellular tissue and fat of 

 the cheeks, run a rapid and destructive course, and may be followed by great dis- 

 figurement and by limitation of the motions of the inferior maxilla. 



Abscesses beneath the buccinator aponeurosis, like fatty growths in the same 

 situation, project towards the cavity of the mouth ; they should be opened through 

 the mucous membrane. 



Fig. 505. 



-rscass**. 



X 



Upper cut edge of masseter 



Temporal — '- 



External pterygoid 



Internal pterygf>i 



Masseter (cut)'^ 



Parotid gland - ->^^ 

 partly removed - _ , 



Sterno-mastoid 



Buccinator 



Posterior fragment 



Line of fracture 

 Anterior fragment 

 Digastric, anterior belly 

 Mylo-hyoid 



Hyo-glossus 



Body of hyoid bone 



Thyro-hyoid 



Omo-hyoid 



Sterno-hyoid 



Dissection of fracture of body of mandible, showing displacement produced by muscular action. 



Over the lower third of the nose the skin is closely adherent, as it is over the 

 chin, where it is also very dense. Infections in those regions are therefore exception- 

 ally painful (page 246). The vascularity and mobility of the skin of the forehead 

 and of the cheeks make it especially useful in plastic operations upon the region of 

 the nose and mouth. 



On account of the rich blood-supply, nsevi are common on all parts of the face, 

 as, by reason of the numerous sweat and sebaceous glands, are acneiform eruptions. 



Lupus and malignant pustule are frequent and grave forms of local infection ; 

 rodent ulcer (epithelioma) is common ; while on the forehead the early syphilitic 

 roseola or papule (corona veneris) and about the lips and nose the later tubercular 

 syphilide are often seen. 



Lipomata, in spite of the considerable quantity of fat in the subcutaneous tissue, 

 are very rare. The mass of fat between the buccinator and masseter muscles — 



