DISSECTION OF THE SUBMAXILLARY REGION. 



parts 

 around it ; 



Dissection 

 to detach 

 mylo-hyoid. 



To see deep 

 muscles saw 

 the jaw, 



fasten 

 tongue, 



and cut 

 mucous 

 membrane. 



Define 

 nerves, 



the opposite side, in a median raphe between the hyoid Lone and 

 the jaw. 



On the cutaneous surface lie the anterior belly of the digastric 

 muscle and the submaxillary gland, the facial artery with its submental 

 offset, and the mylo-hyoid nerve and artery. The fibres of the 

 muscle are frequently deficient near the jaw, and allow the genio- 

 hyoid to be seen. Only the posterior border is unattached, and 

 round it a piece of the submaxillary gland winds. The parts in 

 contact with the deep surface of the muscle will be shown after the 

 undermentioned dissection has been made. 



Action. The mylo-hyoid assists the digastric and genio-hyoid in 

 depressing the lower jaw or in elevating the hyoid bone ; but its 

 principal action is to raise the floor of the mouth and press the 

 tongue against the palate, as in the first stage of deglutition. 



Dissection. To bring into view the muscles beneath the mylo- 

 hyoid, and to trace the vessels and nerves to the substance of the 

 tongue, the student should first divide the facial vessels on the jaw, 

 and remove them with the superficial part of the submaxillary 

 gland ; but he should be careful to leave the deep part of the gland 

 which turns beneath the mylo-hyoid, because the small submaxillary 

 ganglion is in contact with it. Next he should cut through the 

 small branches of vessels and nerve on the surface of the mylo- 

 hyoid ; and detaching that muscle from the jaw, should turn it 

 down (as in fig. 224, p. 624), but without injuring the genio-hyoid 

 muscle beneath it. 



Afterwards the bone is to be sawn through at the symphysis, with- 

 out injuring the muscles beneath it, the soft parts covering the jaw 

 having been first cut. The loose ramus of the jaw (for it has been 

 sawn in the dissection of the pterygoid region) is to be raised to see 

 the parts beneath, and it may be fastened up with a stitch ; but it 

 should not be detached from the mucous membrane of the mouth. 



The apex of the tongue is now to be well pulled out of the mouth 

 over the upper teeth, and fastened with a stitch to the septum of the 

 nose, and the scalpel should be passed from below upwards between 

 the sawn surfaces of the bone, for the purpose of dividing a strong band 

 of the mucous membrane of the mouth ; and it should be carried 

 onwards along the middle line of the tongue to the tip. 



By means of a stitch the hyoid bone may be fastened down, to 

 make tight the muscular fibres. All the fat and areolar tissue cover- 

 ing the parts under cover of the jaw are to be removed, and in doing 

 this the student is to take care of the Whartonian duct, of the hypo- 

 glossal nerve and its branches, which lie on the hypo-glossus muscle, 

 and especially of its small offset ascending to the stylo-glossus muscle ; 

 also of the lingual nerve nearer the jaw. Between the lingual nerve 

 and the deep part of the submaxillary gland the dissector should 

 seek the small submaxillary ganglion with its offsets ; and he should 

 endeavour to separate from the trunk of the lingual the small chorda 

 tympani nerve, and to define the offset from it to the sub- 

 maxillary ganglion. 



