THE THYROID GLAND. 487 



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

 cartilage, to compress the subjacent glands which open 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 

 influence its modulation, or tone. See Mr. Haigton's Essay on 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. r. 



