ANTERIOR TRIANGULAR SPACE. 69 



ANTERIOR TRIANGULAR SPACE. 



This space (fig. 15) contains the carotid vessels and their branches, with 

 many nerves ; and it corresponds with the hollow on the surface of the 

 neck in front of the sterno-mastoid muscle. 



Dissection. To define the anterior triangular space and its contents, 

 take away the deep fascia of the neck, and the fat, but without injuring 

 or displacing the several parts. First clean the surface of the hyoid mus- 

 cles that appear along the middle line, leaving untouched the anterior 

 jugular vein. 



The trunks into which the large carotid artery bifurcates are to be fol- 

 lowed upwards, especially the more superficial one (external carotid), 

 whose numerous branches are to be traced as far as they lie in the space. 

 In removing the sheath from the vessels, as these appear from beneath the 

 muscles at the lower part of the neck, the dissector should be careful of 

 the small descending branch of the hypo-glossal nerve in front of it. In 

 the sheath between the vessels (carotid artery and jugular vein) will be 

 found the pneumogastric nerve, and behind the sheath is the sympathetic 

 nerve. 



Crossing the space, in the direction of a line from the mastoid process 

 to the hyoid bone, are the digastric and stylo-hyoid muscles, with several 

 nerves directed transversely. Thus lying below them is the hypo-glossal 

 nerve, which gives one branch (descendens noni) in front of the sheath, 

 and another to the thyroid-hyoid muscle. Above the muscles, and taking a 

 similar direction between the two carotid arteries, are the glosso-pharyn- 

 geal nerve and the stylo-pharyngeus muscle. Directed downwards and 

 backwards from beneath the same muscles to the sterno-mastoideus, is the 

 spinal accessory nerve. 



On the inner side of the vessels, between the hyoid bone and the thy- 

 roid cartilage, the dissector will find the superior laryngeal 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 ; and on 

 partly displacing it from the surface of the mylo-hyoid muscle, the student 

 will expose the small branch of nerve to that muscle with the submental 

 artery. 



The interval between the jaw and the mastoid process is supposed to be 

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

 facial nerve. 



Limits of the space. Behind, is the sterno-mastoid muscle, l ; and in 

 front, a line from the chin to the sternum, along the middle of the neck. 

 Above, at the base of the space, would be 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. 



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

 above defined, are seen the larynx, and pharynx in part, and many mus- 

 cles converging towards the hyoid bone as a centre, some being above 

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

 hyoid, sterno-hyoid, and sterno-thryoid, 2 to 4 ; and above the os hyoides 

 are the elevator muscles, viz., mylo-hyoid, digastric, ,and stylo-hyoid. Con- 



