Fig. 27. 
ae 
A\\ mpl 
A side view of the larynx, the left wing of the thyroid 
and the mucous membrane removed, and the fibres of 
the arytenoid muscle depressed to expose the liga- 
ments and chink of the glottis. 
__ @, the internal surface of the right wing of the 
thyroid ; 6 b, the arytenoid cartilages ; c, the thyro- 
arytenoid ligament; d, the thyro-arytenoideus 
muscle; d’, the thyro-arytenoideus superior vel 
_ minor; ee, the crico-arytenoidei postici; f, the 
_ crico-arytenoideus Seearal; m, the cricoid carti- 
lage; h, the trachea; J, the external prominence 
of the arytenoid cartilage. 
_ attachment or muscles appropriated to fix it as 
a fulcrum for motions in an opposite sense. 
The crico-arytenoideus lateralis is an irregu- 
Tar quadrilateral muscle, arising from the supe- 
_ ‘ior margin of the cricoid, from thence passing 
_ upwards and backwards, (/; fig. 28). . It is in- 
Serted into the posterior surface of the external 
prominence of the arytenoid cartilage by a tendon 
common to it and the thyro-arytenoid muscle. It 
__ is deeply seated under cover of the thyroid car- 
__ tilage and crico-thyroid muscle. The action of 
4 this muscle has caused much diversity of opi- 
4 nion. Cowper, Haller, Magendie, and others 
consider that it opens the glottis; but Bichat 
; and Sdemmering that it closes it. Its action 
has, however, been mechanically solved in the 
\ following manner by Willis. The arytenoid 
| 
cartilage is loosely fixed to the cricoid by liga- 
_ ments already described at B (figs. 28 and 29). 
The direction of the force of this muscle is 
represented by the line N X (fig. 30), having 
_ its point of insertion into the cricoid about X. 
_ The fibres in passing thence to the arytenoid 
(A, fig. 28) lie nearly parallel to the projection 
_ of the axis of motion, G C; the tension of this 
muscle in the direction N X (jigs. 29 and 30) 
4 
i 
4 
: 
NORMAL ANATOMY OF THE LARYNX. 
Fig. 28. 
107 
iit bh 
he pus! ua 
QZ i 
TT 
te 
wd 
A section of the larynx similar to that of fig. 27, with 
the thyro-arytenvid le 1 d to give a full 
view of the thyro-arytenoid ligaments, and the rima 
glottidis lying in the direction of A and B. 
The line G C is the vertical projection of the crico- 
arytenoid articulating axis; cc, f, g,h, represent 
the same parts as in fig. 27. 
tends to bring N X B into the same straight 
line and approximate the point V to the mesial 
plane; and as N is above the line joining B X, 
it will depress N and still more V, because the 
cartilage turns on the articulating surface be- 
neath Q. The action, therefore, of this muscle 
is to approximate the anterior arytenoid promi- 
nences and depress them. 
The arytenoideus (obliquus and transversus). 
Modern anatomists consider this as one 
muscle, but owing to the obliquity of the fibres 
of one of its fasciculi with respect to the other, 
some have made a division of it into arytenoideus 
obliquus and a transversus. It is a very short 
thick muscle, occupying the concavities on the 
posterior surface of the arytenoid cartilages and 
the interval between them. It consists of two 
layers; the superficial layer, which is composed 
of the oblique fibres, which arise from the base 
of the right arytenoid, and crossing the fibres 
of the deep-seated layer, are inserted into the 
summit of the left arytenoid cartilage: this is 
the arytenoideus obliquus of Albinus. The 
deep-seated layer is thicker and stfonger than 
the superficial; its fibres, which are directed 
transversely from one arytenoid to the other, 
constitute the arytenoideus transversus of Albi- 
nus. The arytenoid muscle is covered pos- 
teriorly with mucous membrane, which is con- 
nected to it by loose cellular substance, in which 
some mucous follicles are found ; anteriorly it 
