THE THYROID GLAND- 487 



to Mr. Hilton, is to approximate the epiglottis and arytenoid 

 cartilage, to compress the subjacent glands which o[)en into the 

 pouch of the larynx, to diminish the capacity of that cavity 

 and to change its form. — 



The extreme irritability of the glottis is unequivocally demonstrated by the 

 cough, which is excited when a drop of water, or any other mild liquid, or a 

 crumb of bread enters it. Notwithstanding this, a flexible tube, or catheter, 

 has several times been passed into the windpipe through the rima glottidis, 

 and been endured by the patient a considerable time. 



The cough, which occurs when these parts are irritated, does not appear to arise 

 exclusively from the irritation of the membrane within the glottis; for, if it 

 were so, mucilaginous substances, when swallowed slowly, could not suspend 

 it. Their effect in relieving cough is universally known ; and as they are 

 only applied to the surface exterior to the glottis, it is evident that the irrita- 

 tion of this surface must also produce coughing. 



Several curious experiments have been made to determine the effect of dividing 

 the different nerves which go to the larynx; by which it appears that the 

 recurrent branches supply parts which are essentially necessary to the forma- 

 tion of the voice ; whilst the laryngeal branches supply parts which merely 

 iniluence its modulation, or tone. See Mr. Haigton's Essay ou this subject : 

 Memoirs of the Medical Society of London, vol. iii. 



The Thyroid Gland, (see fig. 118, p. 454,) 



May be described here, although a part of it is situated 

 below the larynx. 



This body consists of two lobes, which are united at their 

 lower extremities by a portion which extends across the 

 anterior part of the windpipe. Each lobe generally rises 

 upwards and backwards from the second cartilaginous ring of 

 the windpipe over the cricoid cartilage and a portion of the 

 thyroid. It lies behind the sterno-hyoidei, and sterno-thyroidei 

 muscles. It is of a reddish-brown color, and appears to 

 consist of a granular substance ; but its ultimate structure is 

 not understood. It is plentifully supplied with blood, and 

 receives two arteries on each side : one from the laryngeal 

 branch* of the external carotid : and the other from the thyroid 

 branch of the subclavian. 



Notwithstanding this large supply of blood, there is no 



* The main branch from the external carotid, is now more commonly called 

 superior thyroid. — f. 



