THE ANTERIOR PART OF THE NECK 227 



dissection of the contents of the subsidiary parts of the 

 anterior triangle the dissectors of both sides should, together, 

 study the structures which lie in the middle line of the neck 

 and immediately to either side of it ; for this region is of the 

 highest importance to the surgeon. The area is divided by 

 the hyoid bone into supra-hyoid and infra-hyoid portions. 



In the supra-hyoid part lie structures which are concerned 

 in the construction of the floor of the mouth. The dissector 



Occipital triangle 



Subclavian triangle 



Digastric triangle 

 Carotid triangle 



Muscular triangle 



li\\f0 % 



FIG. 92. Diagram to show the Boundaries of the Triangles of the Neck. 



will have noticed already that the fatty superficial fascia is 

 more fully developed here than elsewhere in the neck, and 

 that the anterior margins of the two platysma muscles meet 

 and decussate in the median plane, for about half an inch 

 or so, below the chin. The anterior bellies of the two 

 digastric muscles are attached to the mandible, one on either 

 side of the symphysis. From this they descend towards the 

 hyoid bone, and diverge slightly from each other so as to 

 leave a narrow triangular space, the submental triangle^ be- 

 tween them (Fig. 93). The floor of this space is formed by 

 the anterior portions of the two mylo-hyoid muscles, whilst 

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