THE INFRA-HYOID REGION. 79 



thyro-hyoid membrane and distributed to the mucous 

 membrane of the larynx (vid& Subclavian Artery). 

 This region is of great surgical importance ; as well as 

 being the usual seat of injuries inflicted suicidally or 

 homicidally, the operations of laryngotomy, cricotomy, 

 tracheotomy, and oesoph'agotomy are performed therein. 



Non-surgical wounds, whether suicidal or otherwise, 

 are invariably made across, and, as a rule, the main 

 vascular trunks escape, unless the attempt be very de- 

 termined, for the head is thrown back and these main 

 trunks recede, on the structures beneath the sterno- 

 mastoid being put on the stretch. The usual situation 

 selected for such attempts is the thyro-hyoid space, and 

 the incisions frequently divide the larynx and some 

 branches of the superior thyroid artery, and not un- 

 frequently cut through the base of the tongue and epi- 

 glottis. 



All openings made surgically into the air-passage are 

 made in the middle line, for the very important reason 

 that the muscular coverings of the trachea do not unite 

 in the mesial line, but merely approximate, leaving a 

 cellular interval, through which the windpipe is reached. 

 Unless the middle line be adhered to, although the tra- 

 chea may be opened, great difficulty will probably be 

 experienced in the introduction of the tube, as it will 

 have a tendency to slide between the muscles and the 

 trachea, and miss the opening made in it. Again, sup- 

 posing no difficulty to arise of this nature, the muscle is 

 so much wounded as to be seriously impaired, and may 

 become united to the integument after the tube is re- 

 moved. 



There are three methods by which the windpipe may 

 be opened, viz. : 



