OF THE TRIANGLES OF THE NECK. 459 



brane, and anastomoses in front with the ascending branch of the descending 

 palatine. The external branches, two or three in number, supply the mucous 

 membrane covering the lateral wall of the nose, the antrum, and the ethmoid 

 and sphenoid cells. 



SUEGICAL ANATOMY OF THE TRIANGLES OF THE NECK. 



The student having considered the relative anatomy of the large arteries of 

 the neck and their branches, and the relations they bear to the veins and nerves, 

 should now examine these structures collectively, as they present themselves in 

 certain regions of the neck, in each of which important operations are being 

 constantly performed. 



For this purpose, the Sterno-mastoid, or any other muscles that have been 

 divided in the dissection of the vessels, should be replaced in their normal posi- 

 tion ; the head should be supported by placing a block at the back of the neck, 

 and the face turned to the side opposite to that which is being examined. 



The side of the neck presents a somewhat quadrilateral outline, limited, 

 above, by the lower border of the body of the jaw, and an imaginary line ex- 

 tending from the angle of the jaw to the mastoid process ; below, by the promi- 

 nent upper border of the clavicle ; in front, by the median line of the neck ; 

 behind, by the anterior margin of the Trapezius muscle. This space is subdi- 

 vided into two large triangles by the Sterno-mastoid muscle, which passes 

 obliquely across the neck, from the sternum and clavicle, below, to the mastoid 

 process, above. The triangular space in front of this muscle is called the ante- 

 rior triangle; and that behind it, the posterior triangle. 



ANTERIOR TRIANGULAR SPACE. 



The Anterior Triangle is limited, in front, by a line extending from the chin 

 to the sternum; behind, by the anterior margin of the Sterno-mastoid; its base, 

 directed upwards, is formed by the lower border of the body of the jaw, and a 

 line extending from the angle of the jaw to the mastoid process ; its apex is 

 below, at the sternum. This space is covered by the integument, superficial 

 fascia, Platysma, and deep fascia ; it is crossed by branches of the fascial and 

 superficial cervical nerves, and is subdivided into three smaller triangles by 

 the Digastric muscle, above, and the anterior belly of the Omo-hyoid, below. 

 These smaller triangles are named from below upwards, the inferior carotid, 

 the superior carotid, and the submaxillary triangle. 



The Inferior Carotid Triangle is limited, in front, by the median line of the 

 neck ; behind, by the anterior margin of the Sterno-mastoid ; above, by the 

 anterior belly of the Omo-hyoid ; and is covered by the integument, superficial 

 fascia, Platysma, and deep fascia; ramifying between which is seen the descend- 

 ing branch of the superficial cervical nerve. Beneath these superficial struc- 

 tures, are the Sterno-hyoid and Sterno-thyroid muscles, which, together with 

 the anterior margin of the Sterno-mastoid, conceal the lower part of the common 

 carotid artery. 1 



This vessel is inclosed within its sheath, together with the internal jugular 

 vein, and pneumogastric nerve; the vein lying on the outer side of the artery 

 on the right side of the neck, but overlapping it, or passing directly across it on 

 the left side : the nerve lying between the artery and vein, on a plane posterior 

 to both. In front of the sheath are a few filaments descending from the loop 



1 Therefore the carotid artery and jugular vein are not, strictly speaking, contained in this 

 triangle, since they are covered by the Sterno-mastoid muscle, that is to say, lie behind the 

 anterior border of that muscle, which forms the posterior border of the triangle. But as they lie 

 very close to the structures which are really contained in the triangle, and whose position it is 

 essential to remember in operating on this part of the artery, it has seemed expedient to study 

 the relations of all these parts together. 



