DEMONSTRATIONS Of, <&N ATOMY. 



CHAPTER I. 



DISSECTION OF THE HEAD 



2, 



SECTION I. 



9 



EXTERNAL PARTS OF THE HEAD. 



DIRECTIONS. In the dissection of the head and neck, the student 

 should endeavor to learn the parts described in the first fifty -one pages, 

 before the position of the body is changed ; but if want of time necessitates 

 an omission of some part, the examination of the facial nerve (p. 47) can 

 be best deferred till a subsequent stage. The orbit on one side, the poste- 

 rior triangular space on both sides of the neck, and the exterior and the 

 interior of the head, should be examined whilst the body lies in its first 

 position on the Back, 



Position. The student begins with the dissection of the scalp and the 

 muscles of the ear. To obtain the best position, raise the head to a suitable 

 height, and turn the face to the right side. On the left side the muscles 

 are to be seen, and on the opposite half the vessels and nerves are to be 

 displayed. 



EXTRINSIC MUSCLES OF THE EAR. Three muscles attach the ear to 

 the side of the head. Two are above it, one elevating, the other drawing 

 it forwards ; and the third, a retrahent muscle, is behind the ear. There 

 are other special or intrinsic muscles of the cartilage of the ear, which 

 will be afterwards described. 



Dissection. When the ear has been drawn down by hooks, the position 

 of the upper muscle will be indicated by a slight prominence between it 

 and the head ; and the muscular fibres may be laid bare by means of the 

 two following incisions, made no deeper than the skin : One is to be car- 

 ried upwards on the side of the head, for about three inches, along the 

 cutaneous ridge before mentioned ; and the other, about the same length, 

 is to be directed from before backwards close above the ear, so that the 

 two may join at a right angle. On carefully raising the flaps of skin from 

 below upwards, and removing the subjacent tissue, a thin fan-shaped 

 muscular layer will come into view the more anterior fibres constituting 

 the attrahens, and the posterior the attollens aurem muscle. 



On drawing forwards the ear a ridge marks the situation of the posterior 

 muscle. To remove the integuments, let the scalpel be drawn about an 

 inch behind the ear, from the transverse cut above as far as to a level with 

 2 



