110 
ligamentous fibres of the crico-arytenoid arti- 
culation at B (fig. 30) are relaxed; for, al- 
though some fibres lying nearest the mesial 
plane are directed to draw the arytenoids to- 
wards B, they are counteracted by the fibres 
lying furthest from it, and by assuming the 
whole to act together, the resultant will be as 
nearly as possible "est gona jo to the axis of 
articulation O P, which would open the glottis ; 
and therefore he concludes that the force of the 
thyro-arytenoidei postici in a direction back- 
wards may be neglected. _Bichat erroneously 
considered that they assist the thyro-aryte- 
noidei and crico-arytenoidei in drawing the 
thyro-arytenoid ligaments very tense.* 
The thyro-epiglottidei—These are a pair of 
small muscles situated between the anterior sur- 
face of the thyroid cartilage and epiglottis ; they 
arise from the internal surface of the thyroid 
near its middle, and not far from the origin of 
the thyro-arytenoidei ; their fibres are directed 
upwards and forwards to the base of the epi- 
glottis, to which they are inserted behind the 
ligamenta thyro-epiglottidea. 
Their action is to depress the epiglottis. 
The aryteno-epiglottidei are two small mus- 
cles, arising from the superior pyramid of the 
arytenoid cartilages posterior to the arytenoid 
muscles, or from the fibrous raphé situated 
vertically behind them ; they pass upwards and 
forwards to the sides of the epiglottis, and upon 
the terior border of the thyro-epiglottic 
membrane. 
Action Owing to the direction of their 
fibres, the thyro-and aryteno-epiglottidei tend 
to depress the epiglottis, or rather to effect the 
tension of the aryteno-epiglottic mucous folds. 
The action of the intrinsic muscles of the 
larynx may be briefly recapitulated as follows : 
The crico-arytenoidei postici open the glottis ; 
all the other muscles close it. 
The arytenoideus obliquus and arytenoideus 
transversus approximate the arytenoid cartilages 
posteriorly. The crico-arytenoidei laterales 
and the thyro-arytenoidei bring them in Contact 
anteriorly, The thyro-arytenoidei close the 
centre of the glottis, and with the crico-thyroidei, 
assisted by the sterno-thyroidei, regulate the 
tension, position, and vibrating length of the 
chorde vocales. 
The crico-thyroidei and sterno-thyroidei an- 
tagonise the thyro-arytenoidei, and in stretch- 
ing the crico-thyroid ligament, the sterno-thy- 
roidei with the thyro-arytenoidei antagonise the 
crico-thyroidei. 
The crico-arytenoidei laterales, and thyro- 
arytenoidei, and the arytenoideus obliquus and 
transversus antagonise the crico-arytenoidei 
postici. These last-named muscles likewise 
may be said to antagonize all the muscles which 
close the glottis. 
The genio-glossi, the linguales, the stylo- 
pharyngei, and crico-pharyngei, and hyo-glossi, 
are muscles associated in common with the mo- 
* Qnand les thyro-arytenoidiens et crico-aryte- 
noidiens lateraux d’une part, et les crico-arytenoi- 
diens posterieurs d’une autre part agissent simul- 
tanément, les ligamens thyro-aryténoidiens sont 
fortement tendus. 
NORMAL ANATOMY OF THE LARYNX. 
and larynx, 
belong rather to the structure and functions « 
the two former of these organs than to # 
larynx, and consequently are considered ¢ 
as auxiliary. a 
The motions of the internal mechanis 
the larynx being effected by muse 
forces are directed, with respect to 
in various degrees of obliquity, and in diff 
planes, and producing by their combim 
results which can only be demonstrated on 
chanical principles, it has been deemed des 
ble to introduce them into the preceding it 
tigations to insure greater precision la 
and accuracy of result, and the more espe 
as we find in the works of our best anat 
writers the most discordant opinions, b 
parently upon mere hypothesis or 
observation, and without reference to any ¢ 
or principle from whence their conclusions 
drawn. . 
The perusal of the works of Albinus,* I 
ler,t Cowper,t Séemmering,§ Meckel,|j | 
chat, Magendie,** and Bell,++ confirm : 
remarks ; exceptions to these observations 
found in the works of Borelli,t{ Bart 
and W. Weber,|i|| Bernouilli,{{ 
and Willis;+++ from the invaluable in 
tions of the latter much assistance has b 
rived. 
Bloodvessels.—The arteries of the lai ynx 
derived from the superior thyroid, a branch o 
external carotid and from the inferior thy; 
branch of the subclavian. Small veins 
pany the arteries and empty themselves int 
neighbouring trunks. 4 
Structures called glands—The a 
gland. Syn. Glandule arytenoidee, 
gagni, Bichat, Cloquet; cartilago 
Jormis, Wrisberg, Bandt. The te 
gland is an inappropriate designation gi 
to the cuneiform cartilage by Morgagn 
whose views of the structure of this body 
adopted by Bichat,$§§ Cloquet,|jjj|| and C 
* Historia Musculorum, lib. ii. chap. 2. 
+ Elem. Phys. tom. iii. 
Anat. of the human body. 
De Corporis Hum. Struct. 
tions of the tongue, pharynx, 
Traité Générale, tom. x. 
Traité d’Anat. desc. tom, ii. 
** Physiol. 
tt Anat. of the human body. a 
tt De motu animalium. Lost Batav. 1 
§ Nouvelle mechanique des mouvem 
l’Homme et des Animaux, 1798. 
||| Mechanik der Menschlichen Geh 
mit xvii Taf. Gott. 1836-8. 
44 De motu musculorum. 
*** The muscular motions of the human b 
ttt Cambridge Phil. Trans. 1833. a 
tt} Constant glandule arytenoidee ex g 
substantia é livido albescente, de qua utilem ob 
endo laryngi succum maximé inter ede 
vociferandum, appressa epiglottis; vel 
vicini musculi exprimunt. 
§$§ Il apparoit que les deux glandes a 
ne sont que des glandes muqueuses plus pront 
que celles qui entourent le reste de la 
laryngée, mais qu’elles ont absolument le 
usage. Op. cit. p. 386. 
wil Les glandes sont formées de petits gr 
a assez consistans, d’une cout ris 
p- cit. 
