THE SCALP. 



disinfect them. A cut will open the hair bulbs and sebaceous glands, and, as the hairs 

 project into the subcutaneous tissue, they may serve as a starting point for infection. 



Contraction of the occipitofrontalis muscle may prevent healing in extensive 

 wounds. To avoid this the scalp is covered by a recurrent bandage or otherwise fixed. 



Lacerated wounds do not bleed so freely as do incised wounds, but they are 

 accompanied by a more extensive loosening of the scalp. Large flaps of tissue are 

 frequently raised and turned to one side. The most severe of these injuries have been 

 produced by the hair being caught by a revolving shaft, tearing nearly the whole 

 scalp off. Its loose attachment to the pericranium and bone beneath by the loose 

 subaponeurotic tissue, readily explains the reason of these extensive detachments. 



Contusions cause only a moderate amount of swelling, which is usually circum- 

 scribed. While the skin is not broken, the blood-vessels and other tissues beneath 

 are often ruptured, and, therefore, extravasation of blood occurs. When this is con- 

 fined to the superficial fascia, it is small in amount and limited in area. It does not 

 tend to work its way for any great distance beneath the skin. If the extravasation 

 extends below the aponeurosis, it may cover a considerable area of the skull. When 

 it occurs beneath the pericranium it is called cephalhtzmatoma, or in the new-born 

 capul succedaneum. Caput succedaneum is found almost always on the right side, 

 involving the parietal eminence. It is limited 

 by the attachment of the pericranium at the 

 sutures. 



Hczmatomas of the scalp possess the pecu- 

 liarity of being soft in the centre and sur- 

 rounded by a hard cedematous ring of tissue. 

 In cephalhaematoma of long standing this ring 

 may ossify, and the new bone may even extend 

 and form a more or less perfect bony cyst. 

 This, however, is very rare. 



Haematomas produced by blows on the 

 head are often mistaken for fractures. The 

 raised edge is so hard as sometimes to be 

 thought to be the edge of broken bone. The tis- 

 sues beneath the skin at the site of impact 



seem to be pulpified and remain perfectly soft to the touch; the smooth unbroken 

 skull can usually be felt over an area equal to the site of impact. Surrounding this 

 soft area is the hardened ring, composed of tissues between the skin and the bone, 

 into which serum and blood have been effused. 



Inflammation and abscess are caused by infected wounds, furuncles, erysipelas, 

 caries of the skull and suppurating sebaceous cysts. 



The scalp is a favorite location for erysipelas; if not started primarily by an 

 infected wound, the scalp may be involved secondarily by extension from the face. 



Caries of the skull is often of syphilitic origin. 



Abscesses may occur in three places: 



1. Subcutaneous. 



2. Subaponeurotic. 



3. Subpericranial. 



i. Subcutaneous abscesses are usually small and do not tend to spread but 

 rather to discharge through the skin. This is because the firm fibrous trabeculae 

 prevent lateral extension. Furuncles are quite common in childhood; they are, of 

 course, superficial to the aponeurosis. Sebaceous cysts are especially common in 

 the scalp and they sometimes suppurate. The orifice of the obstructed duct is not 

 usually visible. Sometimes in a small cyst a black spot on its surface indicates 

 the opening of the duct. By means of a needle or pin this opening can be dilated 

 and some of the contents expressed. Of course, if nothing further is done it will 

 reaccumulate. When these cysts become inflamed they become united to the skin 

 above so that it has to be dissected off. If pus forms, it either remains localized to 

 the cyst or bursts through the skin and discharges externally. It does not tend 

 to burrow under the skin laterally on account of the fibrous trabeculae uniting the 



FIG 7. Haematoma on the forehead of a child. 



