THE SCALP. 3 



does not convey much nourishment to it. It is deficient in osteogenetic or bone- 

 forming properties, so that when it is raised off the skull in operations, and the 

 bone removed from beneath, as occurs in trephining, fractures, etc., new bone is not 

 produced. 



The subpericranial tissue is so scanty and loose, particularly in infancy, that 

 it readily allows the pericranium to be raised and effusions to occur beneath. 



THE ARTERIES OF THE SCALP. 



The scalp is supplied by the frontal, supra-orbital, and sometimes a small 

 branch from the lachrymal arteries, from the ophthalmic; by the temporal, through 



Temporal 



Transverse facial 



Posterior auricular 

 Occipital 



FIG. 5. Arteries of the scalp. 



its anterior and posterior branches ; and by the posterior auricular and the occipital 

 arteries from the external carotid. These arteries communicate freely with each 

 other, not only laterally, but also across the top of the scalp. It is not unusual to 

 see a large branch of the temporal communicating directly with the occipital. 



The temporal artery begins in the substance of the parotid gland, just below 

 the condyle of the jaw, and mounts over the zygoma, a centimetre (or less) in front 

 of the ear. It lies on the temporal fascia and its pulsations can be felt at this point, 

 if desired, during the administration of an anaesthetic. About four centimetres ( i ^ 

 in.) above the zygoma, it divides into the anterior and posterior branches. The 

 auriculotcmporal branch of the fifth nerve lies just in front of the ear and between it 

 and the temporal artery. 



The occipital artery mounts to the scalp in the interval between the pos- 

 terior border of the sternomastoid muscle and the anterior border of the trapezius. 

 It is about midway between the posterior border of the mastoid process and the 

 occipital protuberance. If it is desired to expose it from this point forward, the 



