350 
CONTRIBUTIONS TO ZOOLOGICAL PATHOLOGY. 
cartilage and the crico-arytenoid membrane. It arises from the in- 
ternal arytenoid fossa by its radiated margin ; and its fibres, converg- 
ing to a point, form with those of the muscle of the opposite side a 
tendinous arch, or raphe, which stretches across between the opposed 
edges of the arytenoid cartilages, and covers the crico-arytenoid 
membrane. 
7 he aryteno-epiglottideus muscle consists of a thin and mem* 
branous layer of fibres contained chiefly within the aryteno-epiglot- 
tidean fold of mucous membrane, that forms on either side the 
pharyngeal or anterior opening of the larynx. It arises posteriorly 
and superiorly from the anterior margin of the arytenoid cartilage 
and its cuneiform appendage, and, extending forwards and inwards, 
becomes inserted into the side of the epiglottic cartilage and the 
apex of its appendage. Sometimes a few straggling fibres of origin 
come from the inner surface of the great wing of the thyroid car- 
tilage ; and being easily separated from the bulk of the muscle 
during dissection, and then being traced forwards into the ap- 
pendage of the epiglottis as a distinct set of fibres, they have 
received the name of the thyro-epiglottideus, or depressor epiglot- 
tidis. The aryteno-epiglottideus muscle of the horse has its ana- 
logue in man in the aryteno-epiglottideus superior. 
The hyo-epiglottideus , or levator epiglottidis muscle , consists of 
a strong and rounded band of fibres placed in the mesial plane at 
the base of the tongue. It arises from the concavity of the body 
of the os hyoides, behind the attachment of the genio-hyo-glossi 
muscles, and from which it often receives a few fibres, and, passing 
backwards, becomes inserted into the opposed surface of the epi- 
glottic fibro-cartilage, and into the yellow elastic substance that 
forms the hyo-epiglottic ligament. 
Actions. — When the mechanism of the articulation of the cornua 
of the thyroid cartilage with the body of the cricoid is carefully 
examined, it will be observed that there is a striking similarity 
between them and those of the lower jaw, especially between the 
condyloid processes of this latter bone and the concave surface of 
its inter-articular cartilage. 
On moving the thyroid upon the cricoid cartilage it will also be 
seen that the movements are somewhat similar, viz. depression, or 
approximation of the thyroid to the cricoid cartilages, and elevation 
of the former from the latter. In this movement of depression of 
the thyroid cartilage, generally, its anterior margins are carried 
forwards and downwards from the arytenoid cartilages, and con- 
sequently the thyro-arytenoid muscles, anterior and posterior, and 
the elastic tissue and mucous investments of the anterior and 
posterior vocal chords, become elongated from above and behind, 
downwards and forwards, and thus these latter become rendered 
