1112 THE ORGANS OF VOICE AND RESPIRATION. 



an opening is made into the air- passages below. Smaller bodies, such as cherry- or plum-stones, 

 small pieces of bone, buttons, etc. , may find their way into the trachea or bronchus, or may 

 become lodged in the ventricle of the larynx. The dangers then depend not so much upon the 

 mechanical obstruction as upon the spasm of the glottis which they excite. When lodged in the 

 ventricle of the larynx they may produce very few symptoms beyond sudden loss of voice or alter- 

 ation in the voice sounds immediately following the inhalation of the foreign body. When, how- 

 ever, they are situated in the trachea, they are constantly striking against the vocal cords during 

 expiratory efforts, and produce attacks of dyspnosa from spasm of the glottis. When lodged in 

 the bronchus they usually become fixed there, and, occluding the lumen of the tube, cause a loss 

 of the respiratory murmur on the affected side, which is usually the right. 



Beneath the mucous membrane of the upper part of the air-passages there is a considerable 

 amount of submucous tissue which is liable to become much swollen from effusion in inflamma- 

 tory affections, constituting the disease known as "oedema of the glottis." This effusion does 

 not extend below the level of the vocal cords, on account of the mucous membrane being closely 

 adherent to these structures. So that in cases of this disease the operation of laryrigotomy is 

 sufficient. 



Chronic laryngitis, which occurs in those who speak much in public, is known as "clergy- 

 man's sore throat." It is due to the large amount of cold air drawn into the air-passages during 

 prolonged speaking. 



Ulceration of the larynx may occur from syphilis, either superficial or from the softening of 

 a gumma, from tubercular disease (laryngeal phthisis), or from malignant disease (epithelioma). 



The air-passages may be opened in two different situations : through the crico-thyroid mem- 

 brane (laryngotoniy) , or in some part of the trachea (tracheotomy] ; and to these some surgeons 

 have added a third method, by opening the crico-thyroid membrane and dividing the cricoid 

 cartilage with the upper ring of the trachea (laryngo-tracheotomy). 



Larytigotomy is the most simple, and should always be preferred when particular circum- 

 stances do not render the operation of tracheotomy absolutely necessary. The crico-thyroid 

 membrane is very superficial, being covered only in the middle line by the skin, superficial fascia, 

 and the deep fascia. On each side of the middle line it is also covered by the Sterno-hyoid and 

 Sterno-thyroid muscles, which diverge slightly from each other at their upper parts, leaving a 

 slight interval between them. On these muscles rests the anterior jugular vein. The only vessel 

 of any importance in connection with this operation is the crico-thyroid artery, which crosses the 

 crico-thyroid membrane, and which may be wounded, but rarely gives rise to any trouble. The 

 operation is performed thus : The crico-thyroid depression having been felt for and found, a 

 vertical incision is then made through the skin in the middle line over this spot, and carried 

 down through the fascia until the crico-thyroid membrane is exposed. Across cut is then made 

 through the membrane, close to the upper border of the cricoid cartilage, so as to avoid, if pos- 

 sible, the crico-thyroid artery, and a tracheotomy-tube introduced. 



Tracheotomy may be performed either above or below the isthmus of the thyroid body, or 

 this structure may be divided and the trachea opened beneath it. 



The isthmus of the thyroid gland usually crosses the second and third rings of the trachea ; 

 along its upper border is frequently to be found a large transverse communicating branch between 

 the superior thyroid veins ; and the isthmus itself is covered by a venous plexus formed between 

 the thyroid veins of the opposite sides. Theoretically, therefore, it is advisable to avoid dividing 

 this structure in opening the trachea. 



Above the isthmus the trachea is comparatively superficial, being covered by the skin, super- 

 ficial fascia, deep fascia, Sterno-hyoid and Sterno-thyroid muscles, and a second layer of the 

 deep fascia, which, attached above to the lower border of the hyoid bone, descends beneath the 

 muscles to the thyroid body, where it divides into two layers and encloses the isthmus. 



Below the isthmus the trachea lies much more deeply, and is covered by the Sterno-hyoid 

 and the Sterno-thyroid muscles and a quantity of loose areolar tissue in which is a plexus of 

 veins, some of them of large size; they converge to two trunks, the inferior thyroid veins, which 

 descend on either side of the median line on the front of the trachea and open into the innomi- 

 nate veins. In the infant the thyinus gland ascends a variable distance along the front of the 

 trachea, and opposite the episternal notch the windpipe is crossed by the left innominate vein. 

 Occasionally also, in young subjects, the innominate artery crosses the tube obliquely above the 

 level of the sternum. The thyroidea iina artery, when that vessel exists, passes from below up- 

 ward along the front of the trachea. 



From these observations it must be evident that the trachea can be more readily opened 

 above than below the isthmus of the thyroid body. 



Tracheotomy above the isthmus is performed thus : An incision is made from an inch and 

 a half to two inches in length exactly in the median line of the neck from the top of the cricoid 

 cartilage. After the superficial structures have been divided the interval between the Sterno- 

 hyoid muscles must be found, the raphe divided, and the muscles drawn apart. The lower 

 border of the cricoid cartilage must now be felt for, and the upper part of the trachea exposed 

 from this point downward in the middle line. Bose has recommended that the layer of fascia 

 in front of the trachea should be divided transversely at the level of the lower border of the 

 cricoid cartilage, and, having been seized with a pair of forceps, pressed downward with the 

 handle of the scalpel. By this means the isthmus of the thyroid gland is depressed, and is 

 saved from all danger of being wounded, and the trachea cleanly exposed. The trachea is now 

 transfixed with a sharp hook and drawn forward in order to steady it, and is then opened by 



