THE CRANIUM 



1333 



first, in close relation wdth the periosteum. The frontal artery is one of the chief 

 blood-supplies to flaps taken from the forehead. Owing to the paper-like thin- 

 ness of the bones on the medial wall of the orbit, e. g., lacrimal, ethmoid, and 

 body of sphenoid, and the mobility of the skin, injuries which are possibly pene- 

 trating ones, as from a slate-pencil, ferrule, etc., are always to be looked upon with 

 suspicion. After a period of latency of symptoms, infection of the membranes 

 and frontal abscess have often followed. Above the supraorbital margin is the 

 supraciliary arch, and higher still the frontal eminence [tuber frontale]. 



Fig. 1085. — The Skull, showing Kronlein's Method of Craniocerebral Topography; 



THE CRANIUM 



Under this heading will be considered the scalp, the bony sinuses, cranio- 

 cerebral topography and the hypophysis. 



The scalp. — The importance of the scalp is best seen from an examination 

 of its layers (fig. 1086). These are — (1) skin; (2) subcutaneous fat and fibrous 

 tissue; (3) the epicranius (occipito-frontalis) and aponeurosis; (4) the sub- 

 aponeurotic layer of connective tissue; (5) the pericranium. 



The first three layers are connected and move together. The thick skin 

 supported by the dense fibrous subcutaneous laj^er and epicranial aponeurosis, is 

 well adapted to protect the underlying skull from the effects of trauma, and in 

 this connection the mobility of the first three layers on the subaponeurotic areolar 

 tissue is important. A scalp wourd does not gape widely unless it involves the 

 epicranial aponeurosis, in which case it involves the subjacent "dangerous area" 

 of the scalp, so-called because pus in this layer may spread widely underneath 

 the scalp and even give meningeal infection by spreading through the diploic or 

 emissary veins. In the process of scalping (whether performed by the knife or 

 by the hair being caught in machinery), separation takes place at this sub- 

 aponeurotic layer which is loose, delicate and devoid of fat. 



The numerous sebaceous glands frequently give rise to cysts in the scalp. 



