CONTRIBUTIONS TO ZOOLOGICAL PATHOLOGY. 263 
Osseous Mechanism. 
Its osseous mechanism is composed of the following parts : the 
Os hyoides 
Thyroid cartilage 
Cricoid cartilage 
Arytenoid cartilages, with their cuneiform appendages 
Epiglottis, with its lateral appendages. 
The os hyoides is situated at the base of the tongue, and be- 
tween the angles of the rami of the lower jaw. It consists of a 
central portion or body, of two larger cornua, which project up- 
wards and backwards from the body towards the cervical vertebrae, 
and of two smaller cornua, which project upwards and forwards to 
the sides of the base of the tongue, where they articulate with the 
extremities of the styloid processes of the temporal bones. These 
latter processes of the temporal bones have usually been described 
as the appendages to the os hyoides ; but they ought rather to be 
viewed as appendages of the temporal bones, inasmuch as they 
are joined intimately to the latter bones by a strong, though elastic, 
fibro-cartilage ; and to the former by a distinct articulation, pos- 
sessing a synovial membrane. In the human individual they 
correspond to the stylo-hyoid ligaments, which 1 have occasionally 
found so perfectly ossified, as to form, in miniature, a perfect re- 
semblance to these styloid bones. On these considerations, there- 
fore, I have not included these structures as portions of the os 
hyoides. The body of the bone is situated in the mesial plane, 
between the two lesser cornua; and when joined with the greater 
cornua bears a considerable resemblance to a horseman’s spur. 
Its superior and posterior surface is concave, and looks towards 
the epiglottis, to which it is attached by a dense band of yellow- 
elastic ligament; and from its anterior and inferior surface projects 
forwards an elongated and flattened spinous process, to which are 
attached the intrinsic muscles of the tongue, and the elevators and 
depressors of the os hyoides. On the external surface of the body 
are two small condyloid processes, covered with cartilage, for ar- 
ticulating with the lesser cornua, and continued backwards, are 
the greater cornua, flattened upon either side, and terminating 
superiorly and posteriorly in cartilaginous points, which articulate 
by means of strong bands of ligamentous fibres with the anterior 
cornua of the thyroid cartilage. The lesser cornua project up- 
wards and forwards, along the side of the tongue ; their inferior 
extremities being thick and rounded, and articulating by means of 
small facets with the body of the bone ; and their superior extre- 
