i828 HUMAN ANATOMY. 



In the above description we coincide with Onodi,' who denies entirely the existence 

 of the middle laryngeal in man. 



The endings of the numerous sensory nerves in the mucous membrane, as 

 described by Retzius, Fusari, Ploschko, and others, include free terminations between 

 the epithelial cells and subepithelial end-arborizations. According to Ploschko, 

 special end-organs, composed of columnar cells surrounded by delicate nerve-fibrillae, 

 e.xist within the true vocal cords. Taste-buds occur not only on the posterior sur- 

 face of the epiglottis, but also within the laryngeal mucous membrane in the vicinity 

 of the arytenoid cartilages. 



Position and Relations of the Larynx. — The larynx forms a part of the 

 anterior wall of the pharynx and rests, therefore, against its posterior wall. In the 

 adult male the tip of the epiglottis is opposite the lower border of the third cervical 

 vertebra and the lower end of the cricoid opposite some part of the seventh vertebra. 

 Thus in man it covers about four vertebral bodies, with the intervening disks. It is 

 small in the female and rather higher. Mehnert '' believes that in the living body in 

 the upright position the cricoid is about one vertebra lower than it is after death in 

 the recumbent position. Individual variation is marked, as is shown by the results 

 compiled from the researches of Taguki.* Thus in thirty-five men the lower border 

 of the cricoid was opposite or below the seventh vertebra twenty-nine times, but in 

 thirty-three women only twenty-one times. It was above it six times in men and 

 twelve times in women ; in one case (male) it was as high as the fifth vertebra. 



Anteriorly the larynx lies beneath the middle layer of the cervical fascia. The 

 lobes of the thyroid rest on either side against the cricoid and thyroid. The larynx 

 as a whole can be raised and depressed by muscles, and changes its position with the 

 movements of the spine. Thus, when the neck is bent, it falls i cm. , and rises 3 cm. 

 when the neck is extended. When the head is turned to one side, the hyoid is twisted 

 less than the head, but more than the larynx, although the latter and the trachea may 

 share in the movement. The larynx may be displaced sideways by e.xternal pressure. 



Changes with Age and Sexual Differences. — At birth the larynx is very 

 small, but may be said to be relatively larger than later. The sharp angle of the thy- 

 roid cartilage is entirely wanting. The larynx grows gradually up to puberty, when it 

 takes on a sudden expansion, which occurs in both sexes, but is much more marked 

 in the male. According to Luschka, it doubles in man and increases by less than 

 half in woman. The most marked sexual difference is the size and prominence of 

 the thyroid cartilage in the male. The duration of the process by which the larynx 

 of a child changes into that of an adult may, according to F. Merkel, be as much as 

 two years, and, in fact, changes may occur throughout growth. In the foetus the 

 position of the larynx is very high. At birth the lower border of the cricoid is oppo- 

 site the lower border of the fourth vertebra. . Symington found it at six years at the 

 lower border of the fifth and at thirteen at the top of the seventh. Probably it reaches 

 what may be called its permanent position at about puberty. Mehnert, however, finds 

 from his observations on the living that the descent continues till about thirty, when 

 there is a great retardation, or even a suspension, of the process till about sixty, when 

 it goes on again with renewed activity. According to him, the cricoid may ultimately 

 reach the second or even the third thoracic vertebra. It is to be noted that, while 

 the earlier descent is a physiological process, that of old age is a degenerative one, 

 depending in part on changes in the spine and on the loss of elasticity of the tissues. 



PRACTICAL CONSIDERATIONS : THE LARYNX. 



The Air-Passages. — The hyoid bone is closely contiguous to the opening of 

 the larynx, and as its injuries derive their chief surgical importance from that rela- 

 tion, they are considered here. 



Fracture of the hyoid results from compression by the grasp of a hand, by the 

 rope in cases of hanging, or from a direct blow. It usually occurs near the junction 

 of the greater cornu with the body of the bone. Displacement is not apt to be 



^ Die Anatomic und Physiolo.^ie der Kehlkopfnerven, Berlin, 1902. 



' Ueber topographische Altersveriinderungen des Atmungsapparates, 1901, 



» Archiv f. Anat. u. Phys., Anat. Abth., 1889. 



