DEVELOPMENT AND GROWTH OF THE LARYNX. 919 



be seen almost everywhere, excepting upon and near the true vocal cords. 

 They abound particularly upon the epiglottis, in the substance of which are 

 found upwards of fifty small compound glands, some of them perforating 

 the cartilage. Between the anterior surface of the epiglottis, the hyoid bone, 

 and the root of the tongue, is a mass of yellowish fat, erroneously named 

 the epiglottidean gland, in or upon which some real glands may exist. 

 Another collection of glands, named a/rytenoid, is placed within the fold of 

 mucous membrane in front of each arytenoid cartilage, from which a series 

 may be traced forwards, along the corresponding superior vocal cord. The 

 glands of the laryngeal pouches have already been described. 



Vessels and Nerves of the Larynx. 



The arteries of the larynx are derived from the superior thyroid (p. 343), a branch of 

 the external carotid, and from the inferior thyroid (p. 371), a branch of the subclavian. 

 The veins join the superior, middle and inferior thyroid veins. The lymphatics are 

 numerous, and pass through the cervical glands. The nerves are supplied from the 

 superior laryngeal and inferior or recurrent laryngeal branches of the pneumogastric 

 nerves, joined by branches of the sympathetic. The superior laryngeal nerves supply 

 the mucous membrane, and also the crico-thyroid muscles, and in part the arytenoid 

 muscle. The inferior laryngeal nerves supply, in part, the arytenoid muscle, and all 

 the other muscles, excepting the crico-thyroid. 



The superior and inferior laryngeal nerves of each side communicate with each other 

 in two places, viz., at the back of the larynx, beneath the pharyngeal mucous mem- 

 brane, and on the side of the larynx, under the ala of the thyroid cartilage (p. 622). 



DEVELOPMENT AND GROWTH OP THE LARYNX. 



Development. The rudimentary larynx consists, according to Valentin, of two 

 slight enlargements having a fissure between them, and embracing the entrance from 

 the pharynx into the trachea. According to Reichert, the rudiments of the arytenoid 

 cartilages are the first to appear. Rathke, however, states that all the true cartilages 

 are formed at the same time, and are recognisable together as the larynx enlarges, the 

 epiglottis only appearing later. In the human embryo, Fleischmann could not detect 

 the cartilages at the seventh week, though the larynx was half a line in length, but at 

 the eighth week there were visible the thyroid and cricoid cartilages, consisting at 

 that period of two lateral halves, which are afterwards united together in the sixth 

 month. Kblliker, however, states that Fleischmann had been deceived by the presence 

 of a deep groove, and that by making transverse sections he ascertained that those 

 cartilages are single from the first. 



Growth. During childhood the growth of the larynx is very slow. Richerand 

 found that there was scarcely any difference between the dimensions of this organ in 

 a child of three and in one of twelve years of age. Up to the age of puberty the larynx 

 is similar in the male and female, the chief characteristics at that period being the 

 small size and comparative slightness of the organ, and the smooth rounded form of 

 the thyroid cartilage in front. In the female these conditions are permanent, excepting 

 that a slight increase in size takes place. In the male, on the contrary, at the time 

 of puberty, remarkable changes rapidly occur, and the larynx becomes more prominent 

 and more perceptible at the upper part of the neck. Its cartilages become larger, 

 thicker, and stronger, and the alee of the thyroid cartilage project forwards in front so 

 as to form at their union with one another, with an acute angle, the prominent ridge of 

 thepomum Adami. At the same time, the median notch on its upper border is consider- 

 ably deepened. In consequence of these changes in the thyroid cartilage, the distance 

 between its angle in front and the arytenoid cartilages behind becomes greater, and 

 the chordae vocales are necessarily lengthened. Hence the dimensions of the glottis, 

 which, at the time of puberty, are increased by about one-third only in the female, are 

 nearly doubled in the male, and the adult male larynx becomes altogether one-third 

 larger than that of the female. 



Towards the middle of life the cartilages of the larynx first show a tendency to 



