THE ANATOMY OF BIRDS. — OSTEOLOGY. 



151 



through whicli the nerve of sight passes from the brain-cavity to the eye. The black dot a little behind the optic 

 foramen is the oritice of exit of a part of the trifacial nerve. The black mark under the letters '■ on " of the word 

 " frontal " is the olfactory foramen, where the nerve of smell emerges from the brain-box to go to the nose. The 

 nasal cavity is the blank space behind nasal and covered by that bone, and in the oval blank before it. The parts 

 of the beak covered by horn are only premaxillary, nasal, and dentary. The condylt articulates with the tirst 

 cervical vertebra; just above it, not shown, isthe/om/HeM maynum, orgieat hole through which the spinal medulla, 

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

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

 bearing the vomer at its end, is the parasphenoid, <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 basipteryyoUl process, by which tlie 

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

 rostrum. In any Passerine bird, the vomer would be thick in front, and forked behind, riding like the palatine 

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

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

 the paper from the maxillary about where the 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 ; next most so across the bulge of the jugal bar. 



Fio. 63. — Skull of a (\ncV.{Clangulaislandica'i,r\&t. size; Dr. R. "W. Shufeldt, U.S.A. a, premaxillary bone; 

 b, partly ossitieil interna.sal septum; ¥, pervious part of nostril ; c, end of premaxillary, perforated for numerous 

 branches of second division of the fifth cranial nerve ; d, dentary bone of tinder 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 jjrotuberance : ./, vacnity in supraoccipital bone; k, muscular impression on back of skull; I is over the 

 black ear-cavity; m, post-frontal process; n, quadrate bone; o, pterygoid; p, palatine; q, quadrato-jugal ; r, 

 jugal; s, maxillary ; t, fronto-parietal dome of the brain-cavity; w, the lacrymal bone, immense in a duck, nearly 

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

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



Development of the Fowl's Skull (figs. 64 to 69). — In the chick's head cartilage is 

 fcjrmed along the floor of the skull hy the fifth day of incubation. This cartilaginous basilar 

 plate is formed on each side of th notocJiord, fig 64, e (Gr. varov, noton, back ; x°P^^ chorde, a 

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

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

 of the skull as far as the pituitary space, pts. The basilar plate is the p)arachordal (Gr. Trapa, 

 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 canals, hsc. Opposite the end of the notochord, the border of the parachordal plate 

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

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

 passage of the twelfth or hrjpoglossal nerve, q. At each lateral comer is the separate quadrate 

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

 of cartilage, the lingida, Ig (Lat. lingida, a little tongue) with the traheculee, tr (Lat. t)-ahe- 

 cida, a little beam), which enclose the ^;iYM«#rtry space, pts (Lat. pituita, mucus: no applica- 

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



