294 rOEMATION AND GEOWTH OP THE LARYXX. 



wards, along tlie corresponding snperior vocal cord. The glands of the 

 laiyngeal pouches have already been described. 



VESSELS AND NERVES OF THE LARYNX: 



The arteries of the larj-nx are derived from the superior thjTroid, a branch of 

 the external carotid, and from the inferior thyroid, a branch of the subclavian. 

 The reins join the sui^erior, middle, and inferior thyi'oid veins. The Ji/nijjliaties 

 are numerous, and j^ass through the cervical glands. Their mode of distribu- 

 tion resembles that in the trachea. The nrrres are supijlied from the sui^erior 

 larjaigeal and inferior or recurrent laryngeal branches of the xmeumogastric 

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

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

 t.he arytenoid muscle. The inferior laryngeal nerves supply, in part, the arytenoid 

 muscle, and all the other muscles, excepting the crico-tliyroid. 



Tlie superior and inferior laryngeal nerves of each side communicate with each 

 other in two jjlaces, viz., at the back of the larynx, beneath the pharyngeal 

 mucous membrane, and on the side of the larynx, under the ala of the thyroid 

 cartilage. Numerous ganglion-cells are found on the branches, both on those 

 which enter the muscles, and also underneath the mucous membrane. End-bulbs 

 are also described in tlie mucous membrane which covers the posterior or laryngeal 

 surface of the epiglottis (Lindemann). 



The furtlier details of the distribution of the vessels and nerves are to be found 

 elsewhere. 



FORMATION AND GROWTH OF THE LARYNX. 



Tlie rudimentary larynx consists, according to Valentin, of two slight enlarge- 

 ments 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 carti- 

 lages are fonned at tlie same time, and are recognisable together as the larynx 

 enlarges, the epiglottis only ajipearing later. In the human embryo, Fleischmann 

 could not detect the cartilages at the seventh week, though the larjmx was half 

 a line in length, but at the eighth Aveek there were visible the thyroid and cricoid 

 cartilages, consisting at tliat period of two lateral halves, which are afterwards 

 united together in the sixth month. KoUilier, on the other hand, states that 

 those cartilages are single from the first. 



During childhood the growth of the lai-jTix 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 thjToid cartilage in front. In the female these con- 

 ditions are pennanent, 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 Ijecome larger, thicker, and stronger, and the 

 ala3 of the tliAi-oid cartilage project forwards in front so as to form at 

 their union with one another, the prominent ridge of the pomvm Adnvi'i. 

 At the same time, the median notch on its upper border is considerably 

 deepened. In consequence of these changes in the thyroid cartilage, the dis- 

 tance between its angle in front and the aiytenoid cartilages behind becomes 

 greater, and the chordaj vocales are necessai'ily lengthened. Hence the dimen- 

 sions of the glottis, wliich, 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 tlie female. 



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

 ossification ; this commences first in the thyi'oid cartilage, then appears in the 

 cricoid, and lastly in the aiytenoid cartilages. In the thyroid cartilage the ossifi- 

 cation usually begins at the comua and posterior borders; it then gradually 



