THE ANATOMY OF BIRDS. — OSTEOLOGY. 
167 
insertion of the temporal or masseteric muscles which effect closure of the jaw. It is scarcely 
evident in the fowl, fig. 62, but well marked in the duck, fig. 63, over/. At the back of the 
articular surface is the ^pneumatic foramen for entrance of air, when any ; on the inner surface 
of the ramus, about the splenial bone, is the opening conveying the vessels and nerve. 
The Hyoid Bone (Gr. letter v, hu=hy, eldos, eidos, form; figs. 
65-68, 72-74) is the skeleton of the tongue ; a very composite struc- 
ture, consisting of several distinct bones, developed in the second and 
third post.-oral visceral arches (see fig, 65, where ch and bh are the 
original elements of the second arch, making the hasihyal and cerato- 
hyal bones, and 66r, chr, and ebr are the original elements of the third 
arch, making the hasihranchial, cerato-hranchial, and epihranchial 
bones). The whole affair is somewhat ^- or Q-shaped, lying 
loosely, point forward, between the forks of the lower jaw, with its 
long slender prongs curving up behind the hind head more or less ; 
but not definitely connected with any other bones of the skull. The 
connection which exists between the hyoid and other cranial bones 
in a mammal is in birds broken by non-development of certain 
links of bone developed in the mammalian second post-oral arch, as 
the stylo -hyal, epihyal, etc.; though birds have a rudimentary stylo- 
hyal, at least in the embryo, among the several proximal parts of 
the second arch which form the intricate bones Mdthin the ear- 
passages (fig. 67). The visible parts of a bird's hyoid are usually: 
the body of the bone, hasihyal (hh, and fig. 72, c), single and median, 
commonly quite short and stocky, sometimes long and slender. The 
hasihyal bears in front a pair of cerato-hyals {ch; not shown in 
fig. 72, where they have been absorbed in b) usually movably 
articulated with the hasihyal. They commonly appear as little 
" horns " or processes of the next piece, the glosso-hyal (fig. 72, b) 
or bone chiefly supporting the substance of the tongue. It may be 
a stout and apparently single bone, as that of the goose figured ; but 
oftener appears as a pair of slender bones, side by side, whose back- 
ward ends are the cerato-hyals. The glossohyal may or may not 
bear at its fore end a cartilaginous tip, as in fig. 72, a. All the fore- 
going are hyal, i. e., belonging to the second visceral arch ; the 
following are branchial, of the third arch: The basi-branchial 
(bbr, fig. 72, d) is a single median piece, projecting backward 
Fig. 72. 
. •- Hyoid bones of a 
Irom the basihyal, with which it may be perfectly consolidated, as goose, nat. size ; byDr. R. w. 
it is in the figure, or separately articulated ; it may be wanting ; it ^hufeidt, U. S. a. a car- 
' " ' tilaginous end-piece of b, the 
IS usually tipped and prolonged backward with a thread of cartilage, great glosso-hyal, which has 
The hasihranchial is oftener called " urohyaL" but had better be absorbed or replaced cerato- 
n ] X • ^ 1 T . 1 ^ . , hvals or " lesser cornua " ; c, 
allowed its strict morphological name. On either side, the basihyal basihyal, movably articulated 
bears the separately articulated cerato-branchials (cbr, fig. 72, e), ^^^^ ^' ^^^^ combined com- 
1 111 T. , pletely with d, basibranchial, 
long Slender bones diverging as they pass backward, and bearing commonly called " urohyai; " 
upon their ends the epi-branchials (ebr, fig. 72,/), which finish off ceratobranchiai ; /, epi- 
tlie nyoid bone behind, or maybe in turn tipped with cartilaginous gether known as "thyro- 
threads. The cerato- and epi-branchials together are badly called liyals," or " greater cornua." 
the thyro-hyals," and in stiU more popular language the greater cornua" or horns " 
of the hyoid. All these bones vary in different birds in size and shape and relative develop- 
ment ; the branchial elements are the most constant in their length and slenderness. The 
