THORACIC VISCERA OF SOME LARGE MAMMAL 
99 
one upon each side of the prominent median process (“ Adam’s 
apple”) of the thyreoid, with the origin and insertion which is 
indicated by their name; (2) the posterior end of each of the crico- 
thyreoid muscles extending from the posterior edge of the thyre¬ 
oid cartilage to the ventral region of the cricoid; (3) the insertions 
into the lateral surfaces of the thyreoid, of the inferior constrictor 
of the pharynx, which encircles the anterior end of the oesophagus 
and holds it firmly in place; (4) portions of the sternothyreoid 
muscles which have their insertion into the posterior border of 
the thyreoid cartilage. Draw either the ventral or lateral view of 
the larynx and hyoid bone showing this musculature. 
Remove the oesophagus from its attachment to the dorsal 
wall of the larynx by severing the constrictor of the pharynx upon 
each side. Cut transversely across the belly of the thyreohyoid 
muscle upon one side and reflect the two ends of the muscle. 
Make a clean longitudinal cut through the whole length of the 
thyreoid cartilage a little to one side of the midventral line, and 
carefully lift the anterior end of the piece thus separated and free 
it from its loose attachment to underlying parts taking care not 
to destroy the crico-thyreoid muscle, the extensive origin of which 
from the inner surface of the thyreoid will now be fully demon¬ 
strated. With this muscle intact, the detached portion of the 
thyreoid may now be completely reflected, thus making possible 
the dissection of the deeper muscles of the larynx, which should 
be identified from their location and attachment as follows: (1) 
the dorsal crico-arytaenoid or crico-arytaenoideus posterior, 
(2) the lateral crico-arytaenoid, (3) the thyreo-arytaenoid, and, 
(4) the arytaenoid muscles, transverse and oblique, vestiges of 
which may be seen stretching between the anterior ends of the 
arytenoid cartilages. Note, incidentally, that slender muscles 
pass forward from the laryngeal cartilages to the epiglottis. 
Draw a lateral view of this dissection. 
Lay open the larynx by a median incision through its whole 
length along the middorsal line. Note that the vocal folds of the 
mucous membrane, with their underlying elastic ligaments, 
stretch from their ventral attachment to the inner surface along 
the midline of the thyreoid, to the vocal processes of the aryten¬ 
oids, which lie beneath the mucous membrane on either side of 
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