THE NECK. 177 



mencement and tlie large veins at their termination, it ter- 

 minates, forming the two bronchi, round cartilago- elastic 

 tubes running to the lungs. Its last cartilaginous ring is 

 different from the rest, since it forms a species of sac from 

 either side of which a bronchus passes, the right opening 

 being the largest. The trachea therefore passes down 

 the neck slightly inclined to the right side ; superiorly it 

 is in contact with the longi colli muscles, laterally with 

 the carotid arteries, the pneumogastric, recurrent, and 

 sympathetic nerves, and on the left side with the oesophagus. 

 The jugular veins are in contact with its lateral part 

 superiorly and inferiorly, but at the centre are separated 

 by the subscapulo-hyoidei muscles. Sterno-maxillaris and 

 sterno-thyro-hyoideus respectively, by blending with their 

 fellows, help to support it. In passing between the first 

 ribs it is superiorly placed to the commencement portion 

 of the anterior vena cava, and to the termination of the 

 arteriae innominatse, and here the oesophagus passes over 

 it to gain the right side. At its extreme upper -psivt the 

 oesophagus is superiorly placed, and the thyroid bodies on 

 either side generally connected by a central portion which 

 runs round its inferior face. On the inner surface of the 

 trachea, running from one side to the other at its superior 

 3)art, is a continuous layer of transverse unstriated mus- 

 cular fibres termed trachealis transversus ; the outer surface 

 of this muscle is connected to the cartilages by extremely 

 loose areolar tissue, while its inner surface is covered by the 

 mucous membrane which lines the trachea, and which 

 presents ciliated columnar epithelium. The pneumo- 

 gastric nerve, after emerging from the cranium through 

 foramen lacerum basis cranii, and sending numerous fibres 

 to the neighbouring nerves and ganglia, gives off the 

 superior laryngeal nerve ; it then runs down the neck in a 

 sheath with the carotid artery and the recurrent, and sym- 

 pathetic nerves. The recurrent is the inferior laryngeal 

 nerve, and supplies all the intrinsic muscles of the larynx 

 ivith motor poiuer except crico-thyroideus, ivhich receives a 

 branch from the superior laryngeal. The left recurrent 

 nerve is involved in the disease termed " roaring," whence 

 jjaralysis and fatty degeneration of the muscles supplied 

 by it ensues especially of the crico- and thyro-arytenoidei 

 muscles. The superior-laryngeal nerve is compound at 

 its origin ; on arriving at the larynx it supplies some of 



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