102 CLINICAL APPLIED ANATOMY. 



the aponeurosis, which are as follows : the supra-orbital ridges 

 in front, the zygomatic arches laterally, and the superior curved 

 lines behind. 



The arteries found in the scalp are, from the mid-line in front 

 to the mid-line behind, the frontal, the supra-orbital, the anterior 

 and posterior branches of the superficial temporal, the posterior 

 auricular and the occipital. They all run in a direction which is 

 more or less upward, and they freely anastomose with one 

 another. Incisions to free a collection of pus beneath the 

 aponeurosis will have to be planned so as to be vertical, or nearly 

 so, and thus to lie between the scalp arteries. 



In an extensive scalp wound a flap may be raised owing to the 

 great looseness of the tissue beneath the aponeurosis. There is, 

 however, little likelihood of the flap sloughing, because it carries 

 the blood-vessels with it. In the same way, even a large flap 

 turned downwards during various intracranial operations is sure 

 of a good blood supply. 



Scalp wounds caused by even blunt instruments may be very 

 clean cut, because the tissues are stretched as it were over the 

 firm bone beneath when the violence is applied. 



Abscess of the Scalp. A collection of pus above the apo- 

 neurosis of the scalp is like a superficial abscess elsewhere, and 

 may be dealt with in the same manner, due attention being paid 

 to the arteries. 



An abscess beneath the aponeurosis is much more difficult to 

 treat, and requires many incisions owing to its extent. Further, 

 such abscesses may be long in healing, partly due to imperfect 

 drainage and partly to want of rest owing to the activity of the 

 occipito-frontalis muscle. 



The most dependent points for evacuation of the pus vary with 

 the posture of the patient, but the posterior occipital region and 

 the lateral temporal regions are most likely to be the positions 

 that should be selected. Incisions in the frontal region leave 

 very conspicuous scars, in addition to being unsuitable for efficient 

 drainage. 



Hsematoma of the Scalp. Every blow upon the head is liable 



