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 hack 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:=hj, elSos, eidos, form; figs. 

 65-68, 72-74) is the skeleton of the tongue ; a very composite stnic- 

 ture, consisting of several distinct bones, developed in the second and 

 third post-oral visceral arches (see fig. 65, where ch and hh are the 

 original elements of the second arch, making the basihydl and cerato- 

 hyal bones, and bbr, cbr, and ebr are the original elements of the third 

 arch, making the basibrcmehial, cerato-branehial, and epibranchial 

 bones). The whole affair is somewhat J^- 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 skuU. 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 within the ear- 

 passages (fig. 67). The visible parts of a bird's hyoid are usually: 

 the body of the bone, bcesihyal {bh, and fig. 72, c), single and median, 

 commonly quite short and stocky, sometimes long and slender. The 

 basihyal bears in front a pair of cerato-hyals (ch; not shown in 

 fig. 72, where they have been absorbed in 6) usually movably 

 articulated with the basihyal. They commonly appear as little 

 " horns " or processes of the next piece, the ghsso-hyal (fig. 72, 6) 

 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. AH the fore- 

 going are hyal, i. e., belonging to the second visceral arch; the 

 following are branchial, of the third arch : The hasi'branchial 

 (bbr, fig. 72, d) is a single median piece, projecting backward Fio.72.-HyoldboneBof a 

 from the basihyal, with which if may be perfectly consolidated, as goose, nat. size ; byDr. E. W. 

 it is in the figure, or separately aj:tioulated ; it may be wanting ; it Sb«^ U;^S^. A^ ^«>^ <=ar- 

 is usually tipped and prolonged backward with a thread of cartilage, great glosso-hyal, whict has 

 The basibranchial is oftener caUed " urohyal," but had better be ^bsorbed or replaced cerate- 



•' ' hyals or "lesser cornua''; c, 



allowed its strict inorphologieai name. On either side, the basihyal basihyal, movably articulated 



bears the separately articulated cerato-brancMals (cbr, fig. 72, e), ^^^^i^'^JL^^SlcS; 

 long slender bones diverging as they pass backward, and bearing commonly called "urohyal;" 

 upon their ends the epi-brcmcMals (ebr, fig. 72,/), which finish off ^'.J.^'^and/ {«To'l 

 the hyoid bone behind, or may be in turn tipped with cartilaginous gether known as "tbyro- 

 threads. The oerato- and epi-branchials together are badly caUed ^7^^^" <"• " sweater comna." 

 the " thyro-hyals," and in still 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 slendemess. The 



