THE HEAD 219 



Owing to its rich blood-supply, the scalp possesses remarkable 

 vitality. Large areas may be stripped up, and although they 

 may only remain attached by narrow pedicles, if replaced they 

 will heal with little loss from sloughing. 



Vessels and Nerves of the Scalp. The Superficial Temporal Arteries 

 supply the lateral aspects of the scalp and ascend to the vertex to anasto- 

 mose with one another. They divide into frontal (anterior) and parietal 

 (posterior) branches, which communicate freely with the supra-orbital and 

 frontal arteries in the forehead and with the posterior auricular and occipital 

 arteries behind the auricle. The superficial temporal artery is accompanied 

 by the Auricula- Temporal Nerve. 



The Supra-Orbital and Frontal Arteries accompany the Supra-Orbital and 

 Supra-Trochlear Nerves (Fig. 59). They are branches of the ophthalmic 

 artery, which arises from the internal carotid. 



The Posterior Auricular Artery runs backwards and upwards from the 

 external carotid, and lies superficial to the mastoid process. It supplies the 

 auricle and adjoining area of the scalp, and is accompanied by the terminal 

 branches of the Great Auricular (p. 108) and the Lesser Occipital Nerves 

 (p. 108). 



The Occipital Artery (p. 122) supplies the back of the scalp, and its branches 

 accompany those of the Greater Occipital Nerve (p. 138). 



The Galea Aponeurotica (Epicranial Aponeurosis) is a 



thin tendinous sheet which unites the frontal and occipital bellies 

 of the epicranius (occipito-frontalis) to one another. Unless 

 it is cut through in a transverse direction, scalp wounds do not 

 tend to gape. Its lateral margins blend with the strong tem- 

 poral fascia, and, together with the line of origin of the muscular 

 bellies, completely shut in the subaponeurotic space which separ- 

 ates the galea aponeurotica from the pericranium. This space 

 only contains some loose connective tissue and a few small 

 arteries, but it is traversed by the important emissary veins 

 which connect the intra-cranial venous sinuses and the superficial 

 veins of the scalp. When pus collects in this region it can spread 

 in all directions so as to elevate the scalp, which feels to the ex- 

 amining fingers as if it were lying on a water-bed. Incisions for 

 the evacuation of such a collection are made near its lower 

 border and parallel to the larger blood-vessels. The pus may 

 destroy the pericranium and cause necrosis of the bones of the 

 skull ; and it may produce septic thrombosis of the emissary 

 veins, and emboli may spread to the intra-cranial sinuses. On 

 this account the subaponeurotic space is frequently referred to 

 as the Dangerous Area. 



The Venous Return from the Scalp may pass by (i) the 

 extra-cranial or (2) the intra-cranial route. 



I, The extra-cranial route is constituted by the veins corre- 



