THE ANATOMY OF BIRDS.— OSTEOLOGY. 



151 



tlirougli which the nerve of t-iglit passes from the brain-cavity to the eye. The black dot a little behind the oi)tic 

 foramen is the oritice of exit of a part of the trifacUd nerve. The black mark umlcr the letters *■ on " of tlie wurd 

 *' frontal" is the olfactory forainen, where the nerve of smell emerges from the brain-bux to go to the nose. The 

 nasal cavity is the blank .^paco behind nasal and covered by that bone, and in the oval blank before it. The jjarts 

 of the beak covered by horn are only prcmaxiUary, nasal, and dtntary. The comlijle arlicuhites with tlie hrst 

 cervical vertebra; just above it, not shown, is theforamt^t maguuin, or great hole througli whicli the spinal medulla, 

 or main nervous cord, passes from the skull into the spinal column. The hasloccipUal is hidden, excepting its 

 condyle; so is much of the basisphenoUl. The prolongation forward of the basisphenoid, marked " rostrum," and 

 bearing the vomer at its end, is \\iq parasjjhenold, as lar as its thickened under border is concerned. Between the 

 fore end of the pterygoid and the basisphenoidal rostrum, is the site of the baslptcrygotd process, by which the 

 bones concerned articulate by smooth facets; further forward, Ihe palatines ride freely upon the parasphenoidal 

 rostrum. In any Passerine bird, the romer would be thick in front, and forked behind, riduig like the jialatine 

 upon the rostrum. Ttjo palatine seems to run into the maxillary in this view; but it continues on to premaxillary. 

 The maxWo-palatine is an important hone which cannot be seen in the tigure because it extends horizontally into 

 the paper from the maxillary about wlicre ihe reference line " maxillary " goes to that bone. The general line 

 from the condyle to the end of the vomer is the cranial axis, basis cranii, or base of the cranium. This skull is 

 widest across the post-frontal ; uext most so across the bulge of the j ugul bar. 



Fig. 63. — Skull of a duck {Clavgnlaislandica\ nat. size; Dr. K. W. Shufeldt, U. S. A. a. premaxillary bone; 

 6. partly ossified internasal septum ; ?/, X'trvious part of nostril ; c, end of premaxillary. perforated for numerous 

 branches of second division of the fifth cranial nerve; d , dentary bone of under mandible; e, groove for nerves, etc. ; 

 /, a vacuity between dentary and other pieces of the mandible; g. articular surface; h, recurved " angle of the jaw : " 

 i, occipital protuberance: ./, vacuity in supraoccipital bone; /:, muscular impression on back of skull ; / is over the 

 black ear-cavity; m, post-frontal xirocess; n, quadrate bone; o, pterygoid; /;, X'-^ilf-tine; q, quadrato-jugal ; r, 

 jugal; 5. maxillary ; C, fronto-fiarietal dome of the brain-cavity ; w, the lacrymal l>one, immense in a duck, nearly 

 completing rim of the orbit by approaching m\ v, vomer; w, supra-orbital depression for the nasal gland 

 (see p. 157); x, cranio-faeial hinge; y, optic foramen; z, etc., interorbital vacuities. 



Development of the Fowl's SkuU (figs. 64 to 69). — In the chick's head cartilag-e is 

 formed along the floor of the skull by the fifth day of iucubation. This cartilaginous basilar 

 plate is formed on each side of the notochord, fig 64, c (Grr. vwrov, nofon, back ; x^P^'?? c^torde, a 

 chord), a rod-like structure, the primordial axis of the body, around which, along the spinal 

 column, the bodies of the yertebrse are formed, and which runs in the middle line of the floor 

 of the skull as far as the pituitanj space, pts. The basilar plate is ihe para cJiordcd (Grr. irapd, 

 para, by the side of) cartilage. In this, at the earliest stage, are already planted certain parts 

 of the ear, the cochlea, cl, (Lat. cochlea, a snail-shell), and the horizontal one of the three semi- 

 circular cancds, hsc. Opposite the end of the notochord, the border of the parachordal plate 

 is notched, 5 ; this notch afterward forms the foramen ovale, for t]ie passage of parts of the 

 ffth or trifacial nerve. Near the middle line, posteriorly, the plate is perforated for the 

 passage of the twelfth or hyp}Oglossal nerve, q. At each lateral corner is the separate quadrate 

 cartilage, to form the quadrate bone. Anteriorly, the plate connects by a strap or bridge 

 of cartilage, the lingula, Ig (Lat. lingida, a little tongue) with the traheculce, tr (Lat. trabe- 

 cular a little beam), which enclose the pituitary space^ pts (Lat. pituita, mucus: no a])plica- 

 bility here). In front of this pituitary interval the trabeculse come together to form an inter- 



