CONTEXTS OF THE ANTERIOR TRIANGULAR SPACE. 581 



Dissection. To define the anterior triangular space and its Dissection 

 content?, take away the deep fascia of the neck and the subjacent triangie! r 

 i'at, but without injuring or displacing the several parts. First 

 clean the surface of the muscles below the hyoid hone, leaving 

 untouched the anterior jugular vein. 



The trunks into which the large carotid artery bifurcates are to Trace 

 be followed upwards, especially the more superficial one (external Al 

 carotid), the branches of which are to be traced as far as they lie 

 in the space. In removing the sheath from the vessels, as they 

 appear from beneath the muscles at the lower part of the neck, the Seek lougi- 

 dissector should be careful of the small descending branch of the [/ervesj 

 hypogiossal nerve on the surface of the artery. In the sheath 

 between the vessels (carotid artery and internal jugular vein) will 

 be found the pneumogastric nerve, and behind the sheath lies the 

 sympathetic nerve. 



Clean the digastric and stylo-hyoid muscles, which cross the and 

 space in the direction of a line from the mastoid process to the neYves. 

 hyoid bone (fig. 209, p. 573), and beneath them look for several 

 nerves. Thus, crossing the carotid arteries just below the digastric 

 is the hypoglossal nerve, which gives off its descending branch in 

 front of the artery, and further forwards a smaller offset to the 

 thyro-hyoid muscle. Under cover of the muscles, and taking a 

 similar direction between tl*e \wo carotid arteries, are the glosso- 

 pharyngeal nerve and the stylo-pharyngeus muscle. Directed spinal 

 downwards and backwards from beneath the same muscles to the ac 

 sterno-mastoid is the spinal accessory nerve. 



On the inner side of the vessels, between the hyoid bone and Laryngeal 

 the thyroid cartilage, the dissector will find the superior laryngeal n< 

 nerve ; and by the side of the larynx, with the descending part of 

 the superior thyroid artery, the small external laryngeal branch. 



Clean then the submaxillary gland close to the base of the jaw ; Clean gland, 

 and on partly displacing it from the surface of the mylo-hyoid ^myto"" 

 muscle, the student will expose the small branch of nerve to that hyoid. 

 muscle with the submental branch of the facial artery. 



The interval between the jaw and the mastoid process has been 

 already cleaned by the removal of the parotid gland in the dissection 

 of the facial nerve. 



Limits of the space (fig. 211). Behind, is the sterno-mastoid Boundaries, 

 muscle ; and in front, the boundary is formed by a line from 

 the chin to the sternum, along the middle of the neck. Above, at 

 the base of the space, are the lower jaw, the skull, and the ear ; 

 and below, at the apex, is the sternum. Over this space are 

 placed the skin, the superficial fascia with the platysma, the deep 

 fascia, and the ramifications, of the facial and superficial cervical 

 nerves, together with the anterior jugular vein. 



Muscles in the space. In the area of the triangular interval, as Contents of 

 it is above defined, are seen the larynx and pharynx in part, and 

 many muscles converging towards the hyoid bone, some being above 

 and some below it. Below are the depressors of that bone, viz., 

 omo-hyoid, sterno-hyoid, and sterno- thyro-hyoid (- to 4 ) ; and above 



