DISSECTION OF THE HEAD AND NECK. 



181 



If now the inner wing be manipulated, it will be felt to contain a piece 

 of cartilage which begins above in the convex projection close to the 

 upper commissure, extends downwards and round the inferior commis- 

 sure, and terminates in the lower part of the outer ala. This alar car- 

 tilage, when dissected out, displays a close resemblance to a comma, the 

 broad part being placed in the upper part of the inner wing, and the 

 point in the lower part of the outer wing. The cartilages are movably 

 attached by fibrous tissue to the lower extremity of the septal cartilage 

 of the nose, and they give the necessary firmness to the edges of the 

 nostrils, preventing these from falling together in the act of inspiration. 

 The nostrils are covered outwardly by skin continuous with that of the 

 face. This skin, which is 

 thin and adherent to the 

 subjacent textures, is 

 carried round the margins 

 of the alse, and for a short 

 distance into the nasal 

 chamber. If the finger be 

 introduced below the upper 

 commissure, it will be felt 

 to enter a peculiar divertic- 

 ulum termed the false 

 nostril. This blind pouch 

 extends upwards for about 

 four inches, and it is lined 

 by a continuation of the 

 skin. If the wings of the 

 nostril be separated as 

 widely as possible, the 

 opening of the lachrymal 

 duct will be seen a few 



inches within the lower commissure. The orifice is circular, appearing 

 as if a small piece of skin had been punched out. # Just beyond the 

 orifice the skin is continued by the mucous membrane of the nasal 

 chamber, which is distinguished from the common integument by 

 being non-pigmented, vascular-looking, and destitute of hairs. 



Directions. — The skin on the face should be entirely removed. Over 

 the lips and false nostril care is necessary to avoid going deeper than 

 the skin. One side should first be used for the muscles, and then the 

 vessels and nerves should be dissected on the opposite side. 



The muscles now to be dissected include a series of thin muscles 

 which terminate in and move the lips and nostrils; the buccinator, 

 which forms the basis of the cheek ; and the masseter,. a powerful 

 muscle of mastication, covering the vertical ramus of the lower jaw. 



Fig. 22. 



1, 1. Comma-like cartilages of the nostril ; 

 2. Septal cartilage. 



