CONTRIBUTIONS TO ZOOLOGICAL PATHOLOGY. 349 
The ihyro-arytenoideus superior, or anterior muscle ( the liga- 
mento-arytenoideus superior of Youatt^, is a strong and flattened 
band of muscular fibres, situated immediately external to, and 
covered by, the fold of mucous membrane that constitutes the ante- 
rior chorda vocalis, and forms the anterior boundary of the ven- 
tricle of the larynx. Anteriorly and inferiorly it arises from the 
inner surface of the angle of the thyroid cartilage, immediately 
beneath and behind the pedicle of the epiglottis ; and passing up- 
wards and backwards, parallel to the anterior vocal chord, it becomes 
inserted into the external arytenoid fossa, near the apex of the car- 
tilage, and where its fibres become also amalgamated with those 
of the thyro-arytenoideus transversus. 
This muscle is the analogue of the aryteno-epiglottideus inferior 
in man. 
The thyro-arytenoideus inferior > or posterior muscle ( the liga- 
mento-arytenoideus inferior of Youatt), is situated at the posterior 
and inferior part of the proper cavity of the larynx, and is imme- 
diately covered by the mucous membrane and elastic tissue of the 
posterior or true vocal chords. From the former muscle it is sepa- 
rated by a considerable quantity of loose areolar tissue, in which is 
expanded the mucous membrane that forms the ventricle of the 
larynx. In form it is broad and elongated, thicker and firmer above 
and behind, and rather loose and opened out before. It arises an- 
teriorly from the inferior edge of the angle of the thyroid cartilage 
and the laryngeal surface of the convex edge of the crico-thyroid 
membrane ; and passing upwards and backwards, parallel with but 
a little behind the longitudinal axis of the true vocal chords, 
becomes inserted into the entire surface of the external arytenoid 
fossa. Some anatomists have considered this muscle as being only 
a portion of the crico-arytenoideus lateralis ; but I have always 
found it to be distinct in its course and attachments*. 
The thyro-arytenoideus transversus, or brevis muscle, is short 
in length compared to the two former muscles, and is situated in 
the space between the superior edge of the thyroid cartilage and 
the external surface of the crico-arytenoid articulation. It arises 
from the superior margin of the thyroid cartilage, immediately 
behind its anterior cornu, and, proceeding horizontally backwards 
and inwards, becomes inserted, partly into the vertical crest on 
the superior surface of the arytenoid cartilage, but principally into 
the central tendinous raphe formed by the junction of the mesial 
edges of the arytenoid muscles. 
The arytenoideus muscle consists of a radiated and triangular 
fasciculus of fibres placed on the superior surface of the arytenoid 
* Vide Cruvelhier’s Descriptive Anatomy, vol. i, page 569. 
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