THE SCALP. 25 



the one hand, and the laxity of the subepicranial tissues upon the other, are responsible for the 

 fact that cutaneous wounds, in which the aponeurosis is not divided, do not gape, in contradis- 

 tinction to cutaneous wounds in other regions. Gaping occurs only when the aponeurosis, and 

 consequently the entire thickness of the scalp, has been divided. Wounds at right angles to the 

 direction of the fibers of the occipitofrontalis gape more than those made in a sagittal direction. 

 Owing to the dense connective tissue intimately uniting the skin and galea aponeurotica, and the 

 consequent loss of elasticity, large cutaneous defects cannot be covered, since it is impossible to 

 bring the edges of the wound together. In contrast to effusions of blood in the loose subepi- 

 cranial tissue, ecchymoses in the dense subcutaneous tissue are not very extensive, but give rise 

 to circumscribed swellings. 



-- Sebaceous glands 

 Cerium 

 Hair-follicle 



Subcutaneous fatty tissue 



: -==-Retinacula 



Artery 



Galea aponeurotica 5 



Subepicranial tissue 



Pericranium 



External plate 



Diploe 





Internal plate 

 Dura mater 



FIG. 6. A cross-section of the layers of the scalp and of the cranium. 



The same condition of affairs is noted in purulent inflammations, since suppuration in the 

 scalp does not become diffuse, while suppuration beneath the scalp may continue to extend until 

 its progress is arrested at the supraorbital margins, the zygoma, and the superior curved line of 

 the occiput. In such cases an early and deep incision is necessary, since spontaneous perforation 

 through the firm and dense scalp is not to be expected. 



The scalp is more liberally supplied with blood than any other cutaneous area. In this 

 situation, in contrast to the usual relation, large vessels are found in the subcutaneous connective 

 tissue. These arteries are so firmly imbedded in this dense tissue that it is quite difficult to pick 

 them up with a hemostat after division, and the hemorrhage must frequently be arrested by 

 suture. The arterial anastomoses are so numerous that they form a large-meshed network of 

 arteries which is spread out upon the galea aponeurotica (see Plate 2). Every portion of the 



