SECTION X 



ON SURGICAL 



AKD 



TOPOGRAPHICAL ANATOMY 



By W. H. a. JACOBSON, M.Ch.Oxon. 



ASSISTANT SURGEON, GUY'S HOSPI-TAL 



SUPERFICIAL ANATOMY OF THE HEAD AND NECK 



THE CRANIUM AND SCALP 



Bony landmarks. — These should be studied with the aid of a skull, as well 

 as on the living subject. In the middle line, behind, is the external occipital pro- 

 tuberance, or inion, the thickest part of the vault, and corresponding internally 

 with the meeting-point of six sinuses. From this point the superior curved lines 

 pass out towards the mastoid processes, and indicate the first part of the course of 

 tlie lateral sinuses, which, after running horizontall}^ outwards, turn downwards in 

 the mastoid bone. The position of these important vessels would be more cor- 

 rectly indicated by a line drawn first from the external occipital protuberance to 

 the upper border of the mastoid process, one inch behind the external auditory 

 meatus. This line gives the transverse and longer part of the sinus. A shorter line, 

 from the ending of the first to tlie i\]) of the mastoid, will indicate by its upper 

 two-thirds the sigmoid portion of the sinus and the bend by wliich it communi- 

 cates with the transverse part (Macewen). (Fig. 660.) 



About two inches and three-quarters (68 mm.) above the external occi])ital pro- 

 tuberance is the lambda, or meeting of the sagittal and lambdoidal sutures (i)oste- 

 rior fontanelle, small and triradiate in shape). It is useful to remember, as guides 

 on the scalp to the al)ove two important points, that the lambda is on a level 

 with the supraciliary ridges, and the external occipital protuberance on one with 

 the zygomatic arches. 



The point of junction of the lambdoidal and S(]uamous sutures, the asterion, 

 is placed about three-cjuarters of an inch liehind and half an inch above the upjicr 

 part of the posterior border of the mastoid (fig. 659). The bregma, or junction 

 of the coronal, sagittal, and, in early life, the frontal suture (anterior fontanelle, 

 large and lozenge-shaped), lies just in front of the centre of a line drawn trans- 

 versely over the cranial vault from one preauricular point to the other (fig. 659). 

 The pterion, or junction of the frontal, parietal, temporal, and sphenoid bones, 

 lies in the temporal fossa, one and a half to two inches behind the external angular 

 process of th-e frontal, and about the same distance above the zygoma (fig. 659). 

 This spot also gives the position of the trunk and the anterior and larger division 

 of the middle meningeal artery. The zvgoma can be traced backwards to its roots 



1080 



