236 
DES. A. CAETE AND A. MACALISTEE ON THE 
united to its fellow of the opposite side, forming the median isthmus before mentioned, 
while the latter, which measured about 2 inches in length, was free, smooth, and sepa- 
rated from the corresponding portion of the opposite side by a deep triangular notch, 
which at its posterior extremity measured 1 \ inch in breadth. The inferior or superficial 
surface was flat, and exhibited the attachments of three muscles along its outer margin ; 
of these the thyrohyoid was most anterior, the cricothyroid most posterior, and the 
sternothyroid intermediate. 
The upper or deep-seated surface corresponded to and covered the upper third of the 
inferior surface of the great laryngeal pouch, to be hereafter noticed, and posteriorly it 
came into contact with the outer surface of the arytenoid cartilage ; its central portion 
in front gave origin to the thyro-arytenoid muscle, and posteriorly to a few of the an- 
terior fibres of the constrictor of the laryngeal pouch. 
The cricoid cartilage, in outline, was irregularly rhomboidal, representing about two- 
fifths of a circle, and formed the inferior boundary of the posterior three-fourths of the 
larynx. It presented two surfaces, which were bounded by four irregularly shaped edges 
and angles. The superior surface presented on each side a slight concavity, from which 
the crico-arytenoideus posticus took its origin, and in the central line it was transversely 
concave to accommodate the passage of the oesophagus ; the inferior surface was the 
reverse shape of the superior, i. e. concave on each side and convex on the central line ; 
to this latter part the mucous membrane of the posterior three-fourths of the larynx was 
closely adherent. The centre of the anterior edge presented a slight concavity, to which 
the posterior edge of the arytenoideus proprius was attached. The posterior margin 
was extremely irregular in outline, presenting in the median line a tongue-shaped pro- 
cess, which was directed backwards towards the first ring of the trachea. The outer 
edge was slightly convex, where it gave origin to the cricothyroid muscle. The ante- 
rior and external angle formed a facet for articulating with the arytenoid cartilage ; the 
posterior angle extended backwards, terminating in a flat process ; and about 1 inch in- 
ternal to this a small tubercle was situated, to which the inferior cornu of the thyroid 
cartilage was articulated by the interposition of strong fibrous tissue. 
The arytenoid cartilages were extremely irregular in shape ; each of them consisted of 
a body or central part and two processes ; the body had three surfaces, an external, in- 
ternal, and posterior; the first was enlarged by the projection of a prominent shelf-like 
process along its lower and outer border, from this the upper fibres of the constrictor of 
the laryngeal pouch arose. 
The internal surface of the cartilage was convex, presenting on the middle of its pos- 
terior border an oval concave articular facet, which measured 1^ inch in length by \ an 
inch in width ; this was articulated with a convex surface placed on the outer edge of 
the posterior and lateral aspect of the cricoid cartilage, and was lined by synovial mem- 
brane and surrounded by a capsular ligament. The superior surface was somewhat 
triangular, and of much less extent than either of the other two ; it lay in front and above 
the articular surface just described, and was covered by the crico-arytenoideus posticus 
