GENERAL ORNITHOLOGY 



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Fig. 62.— Skull of common fowl, enlarged ; from nature by Dr. R. W. Shufeldt, U.S.A. The 

 names of bones and some other parts are printed, requiring no explanation : but observe the 

 following points : The distinction of none of the bones composing the brain-case (the upper 

 back expanded part) can be found in a mature skull. The brain is contained between the 

 occipital, sjjhenoidais, squamosals, parietah, and part of frontal; the ethmoidals belong to the 

 same group of cranial bones proper. All other bones, excepting the three otic ear-bones, are 

 bones of the face and jaws. The lower jaw, of live bones, is drawn ili-tadu'd ; it articulates by 

 the black surface marked articular with the prominence just abovi'- tlir iiimilraie bojie. Ob- 

 serve that from this quadrate a series of bones — quadrato-jiigcd, jugal, 'tiinxillnnj -makes a slender 

 rod running to the premaxillary ; this is the zygoma, or jugal liar. Observe from the quadrate 

 also another series, composed oi pterygoid and palatine bones, to the premaxillary ; this is the 

 pterygo-pcdatine bar ; it slides along a median fixed axis of the skull, the rostrum, which bears 

 the loose vomer at its end. The under mandible, quadrate, pterygoid, and vomer are the only 

 movable bones of this skull. But when the quadrate rocks back and forth, as it does by its 

 upper joint, its lower end pulls and pushes upon the upper mandible, by means of the jugal 

 and pterygo-palatine bars, setting the whole scaffolding of the upper jaw in motion. This 

 motion hinges upon the elasticity of the bones of the forehead, at the thin jilacejust where the 

 reference-lines from the words "lacrymal" and " mesethmoid " cross each other. The dark 

 oval space behind the quadrate is the external orifice of the ear ; the parts in it to whi(:h the 

 three reference-lines go are diagrammatic, not actual representations ; thus, the quadrate 

 ai'ticulates with a large pro-otic as well as with the squamosal. The great excavation at the 

 middle of the figure, containing the circlet of unshaded bones, is the left orbital cavity, orbit, or 

 socket of the eye. The mesethmoid includes part of the background of this cavity, shaded dia- 

 gonally. Tlie upper one of the two processes of bone extending into it from behind is the post- 

 frontal ox sphcnolic process ; the under one (just over the quadrate) is the squamosal process. A 

 bone not sliown, the presphenoid, lies just in front of the oval black space over the end of 

 basisphenoid. This black oval is the optic foramen, through which the nerve of sight passes 

 from the brain-cavity to the eye. The black dot a little behind the optic foramen is the orifice 

 of exit of a part of the trifacial nerve. The black mark under the letters " on " of the word 

 " frontal " is the olfactory foramen, wliere 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, 

 luisal, and dentary. The condyle articulates with the first cervical vertebra ; just above it, not 

 shown, is the foramen magnum, or great hole through which the spinal medulla, or main 

 nervous cord, passes from the skull into the spinal column. The basioccipital is hidden, ex- 

 cepting its condyle ; so is much of the basisphenoid. The prolongation forward of the basi- 

 sphenoid marked "rostrum," and bearing the vomer at its end, is the parasphenoid, as far as 

 its thickened under border is concerned. Between the fore end of the pterygoid and the basi- 

 sphenoidal rostrum, tis the site of the basipterygoid process, by which the bones coneei-ned articu- 

 late by smooth facets ; further forward, the palatines ride freely upon the paiasphenoidal 

 rostrum. In any Passerine bird, the vomer would be thick in front, and forked beliind, 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 maxillo-palatine is an important bone which 

 cannot be seen in the figure 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. 



