THE ANTERIOR PART OF THE NECK 129 



of the omo-hyoid muscles. In the median intermuscular 

 interval the following structures will be found : (i) the median 

 part of the thyreo-hyoid membrane ; (2) the anterior border 

 of the thyreoid cartilage, with the projecting prominentia 

 laryngea (O.T. pomum Adami) at its upper end; (3) the 

 arch of the cricoid cartilage ; (4) the crico-thyreoid ligament, 

 with the anastomosis between the crico-thyreoid arteries, and 

 the anterior ends of the crico-thyreoid muscles ; (5) the first 

 ring of the trachea, with the anastomosis between the medial 

 terminal branches of the superior thyreoid arteries ; (6) the 

 isthmus of the thyreoid gland ; (7) the inferior thyreoid veins, 

 and (8) the lower cervical rings of the trachea. Occasionally 

 the third or middle lobe of the thyreoid gland and the 

 levator glandulae thyreoideae, or one or other of them, is found 

 extending upwards from the isthmus of the thyreoid gland. 

 When it is present the middle lobe either terminates above 

 ma pointed extremity or becomes continuous with a fibrous 

 cord, the remains of the thy reo- glossal duct, which disappears 

 in the region of the hyoid bone. The levator extends from 

 the isthmus or from the third lobe, and is attached, above, to 

 the lower border of the hyoid bone. 



Dissection. The superficial layers of the deep fascia must 

 now be removed from the whole area of each anterior triangle, 

 and for that purpose, and for the satisfactory dissection of the 

 contents of the triangles, it is necessary that the head be turned 

 well over to the opposite side ; therefore the dissectors must 

 arrange to work alternately. 



Commence with the digastric triangle. Its boundaries are 

 the lower border of the mandible and the two bellies of the 

 digastric muscle. 



Its contents are: (i) the lower part of the submaxillary 

 gland; (2) the submaxillary lymph glands; (3) part of the 

 external maxillary artery ; (4) part of the anterior facial vein ; 

 (5) the mylo-hyoid nerve; (6) the mylo-hyoid artery; (7) a 

 small part of the hypoglossal nerve ; (8) a small part of the 

 lingual vein. 



Dissection. Remove the deep fascia which was previously 

 turned aside (p. 123) and clean the submaxillary lymph glands. 

 Most of those glands lie immediately below the mandible, in 

 the angle between it and the submaxillary gland, but some may 

 be found on the superficial surface of the gland. Turn the gland 

 upwards and fix it with hooks ; then secure the mylo-hyoid 

 nerve and artery, as they enter the posterior border of the 

 anterior belly of the digastric about the middle of its length, 

 VOL. Ill 9 



