268 
CONTRIBUTIONS TO ZOOLOGICAL PATHOLOGY. 
synovial membranes, which permit a considerable degree of de- 
pression and elevation to take place between them. 
The crico-thyroid articulation. — The cricoid is articulated to 
the thyroid cartilage at two points; first, between the alee of the 
thyroid and the opposed margin of the cricoid, forming the crico- 
thyroid space ; and, secondly, upon either side, by the posterior 
cornua of the thyroid and the sides of the body of the cricoid. 
The first of these, the middle crico-thyroid articulation, is formed 
of a thick and very strong yellow elastic filament, attached, be- 
hind, to the edge of the cricoid cartilage, and before, to the inner 
surface of the angle and the great wings of the thyroid. Upon its 
inferior surface lie the crico-thyroidei muscles, having a space, 
however, between them, which is separated from the integument 
by the mesial edges of the sterno-hyo-thyroidei muscles. Its 
superior surface is covered by the mucous membrane of the 
larynx, and its margins give a partial attachment to the inferior 
thyro-arytenoid muscles. The lateral crico-thyroid articulations 
belong to the ginglymoid variety of the diarthrodial class of arti- 
culations, and resemble in miniature that of the lower jaw. The 
condyloid processes, or posterior cornua, of the thyroid cartilage 
are surrounded by capsular ligaments, thicker and stronger upon 
their external surfaces, and which ligaments are also attached to 
the margins of the glenoid cavities on the sides of the body of the 
cricoid. Internally there are cartilages of incrustation and dis- 
tinct synovial membranes. The movements of this articulation are 
depression and elevation of the thyroid from the cricoid carti- 
lages; these are best seen if the larynx be removed with its 
ligaments entire, and then reversed in its position, when the 
greatest resemblance will be observed between the movements of 
this and those of the temporo-maxillary articulation. 
The crico- arytenoid articulations. — The oblique articular sur- 
faces on the anterior margin of the body of the cricoid cartilage 
are received into corresponding depressions in the bases of the 
arytenoids. These are surrounded by capsular ligaments, the 
crico-arytenoids, and internally each is lined by a distinct syno- 
vial membrane. The movements of these articulations consist of 
oblique eversion and inversion of the arytenoid cartilages. The 
axis of this latter movement, if carried forwards, would pass along 
the opposite side of the epiglottis ; as, for example, if the right 
arytenoid cartilage was carried forwards into the anterior aperture 
of the larynx, its apex would pass in the direction of the left side 
of the epiglottis. Besides these ligaments, there is another strong 
band of yellow elastic tissue, stretching between the anterior edge 
of the body of the cricoid cartilage and the bases, and opposed 
edges of the arytenoids. This membrane I would denominate 
