CHAPTER IX. 



DISSECTION OF THE HEAD AND NECK. 



SECTION I. 



EXTERNAL PARTS OF THE HEAD. 



Directions. In the dissection of the head and neck, the student Parts to be 

 should learn the parts described in this and the following Section, JjJJ^Jy J 



whilst the bodv is in the lithotomy position during the first three in the 



. ,. ." lithotomy 



days or dissection. position. 



The scalp is properly limited inf eriorly, from behind forwards, by Limits of 

 the external occipital protuberance, the superior curved line of the the scal P- 

 occipital bone and its prolongation along the temporal bone down 

 to the tip of the mastoid process, by the temporal ridges on the 

 parietal and frontal bones and by the supra-orbital margin ; but the 

 dissection in this section extends downwards to the upper border 

 of the zygoma. 



Cha.racteristics of the part. The skin of the scalp is firmly con- Tough sub- 

 nected to the subjacent muscular and aponeurotic structures, and time. 

 instead of the intermediate tissues consisting, as they do in most 

 parts of the body, of a relatively loose, subcutaneous fascia, they are 

 composed of dense tissue uniting the parts together. In this dense 

 tissue the superficial nerves and vessels run ; the roots of the hairs 

 project into it, and contained in its interstices is a certain amount 

 of yellowish, fat. It is an easy thing to reflect the skin, the super- 

 ficial vessels and nerves and the aponeurotic tissues in a single 

 layer, especially towards the upper part of the head. In order to Caution, 

 avoid this the student should be very careful to keep the knife 

 well directed to the skin, cutting through the hair roots, and as 

 much as possible he should dissect from below upwards, for the 

 blood vessels and nerves are larger below and smaller above. 



Position. The body having been placed on its back in the lithotomy 

 position, the head should be raised to a suitable height by blocks 

 under the neck, and the face turned towards the opposite side Position, 

 this latter being done by mutual arrangements between the 

 dissectors of the two sides. 



Dissection. An incision should be made upwards behind the 

 auricle along the line of its attachment, from the tip of the mastoid 

 process below to the upper border of the auricle above, and it 

 should then pass down the anterior attachment as far as the upper 

 border of the zygoma. From this it should be prolonged forwards 



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