Lect. IL] 



HINGING OF THE LOWER JAW. 



39 



shows liow tills Is done, and why the feat of fly-catching 

 is so difficult in the dog trying to sleep in the sun, but 

 kept awake by teasing flies. 



In the Duchhill, as in mammals generally, the pier 

 or hinge-piece is gone, and the maxilla inferior (or 



af- '-^ HJ 



Fig. 4a. 



Fig. 4. 



Fig. 4. — Skull of Common Fowl {Gcdlm domesticus) o\x&-'hsM larger than specimen. 

 px, premaxillary; mx, maxillary; v, vomer; n, nasal; cth, ethmoid; /, lacrymal ; 

 pe, perpendicular ethmoid ; x>^j presphenoid ; I, olfactory nerve ; io.s, interorbital 

 space ; os, orbitosphenoid ; /, frontal ; pf, post-frontal ; p, parietal ; sq, squamosal ; 

 s.o, superoccipital ; j.p, jugal x>rocess of squamosal ; co, exocciptal, V, 5th nerve ; 

 11, optic nerve ; ty.c, tympanic cavity ; 5^, basi-temporal ; q, quadrate ; pg, ptery- 

 goid ; pa, palatum ; j, jugal ; qj, quadrate-jugal ; p.ap, posterior angular process ; 

 icLp, internal angular process ; ar, articular ; ag, angular ; sa.g, supra-angular ; 

 cl, dentary. 



Fig. 4a. — Auditory Columella of Fowl, magnified 6 diameters, and sho"\\Ti from the 

 inside and end. 



mandible) is hinged directly to the temporal bone, a solid 

 part of the strong skull- wall. What has become of the 

 '' OS qiiadratum,'' as the bird's jaw-pier is called? The 

 answer is, that in the mammal there takes place a 



