4 SURGICAL APPLIED ANATOMY. [Chap. i. 



glove when it is tightly stretched over the knuckles, 

 and those parts are sharply rapped. 



The scalp is extremely vascular, and presents there- 

 fore a great resistance to sloughing and gangrenous 

 conditions. Large flaps of a lacerated scalp, even 

 when extensively separated and almost cut off from 

 the rest of the head, are more prone to live than to 

 die. A like flap of skin, separated from other parts of 

 the surface, would most probably perish ; but the 

 scalp has this advantage, that the vessels run practi- 

 cally in the skin itself, or are, at least, in the tissue 

 beyond the aponeurosis (Fig. 1). Thus, when a scalp 

 flap is torn up, it still carries with it a very copious 

 blood-supply. Bleeding from these wounds is usually 

 very free, and often difficult to arrest. This depends, not 

 so much upon the number of vessels in the part, as 

 upon the density of the tissue through which these 

 vessels run, the adherence of the outer arterial wall to 

 the scalp structure, and the inability, therefore, of the 

 artery to properly retract when divided. 



In all parts of the body where a dense bone is 

 covered by a comparatively thin layer of soft tissues, 

 sloughing of those tissues is apt to be induced by 

 long and severe pressure. The scalp, by its vascu- 

 larity, is saved to a great extent from this evil, and is 

 much less liable to slough than are the soft parts 

 covering such bones as the condyles of the humerus or 

 the sacrum. But such an effect is sometimes pro- 

 duced, as in a case I saw, where the tissues over the 

 frontal and occipital regions sloughed from the con- 

 tinued application of a tight bandage put on to arrest 

 bleeding from a frontal wound. 



The pericranium is but slightly adherent to 

 the bone, except at the sutures, where it is intimately 

 united. In lacerated wounds this membrane can be 

 readily stripped from the skull, and often, in these 

 injuries, extensive tracts of bone are laid bare. The 



