ANA TOMY OF BIRDS 



5. THE SKULL 



The Skull of a Bird is a poem in bone — its architecture is the 

 " frozen music " of morphology ; in its mutely eloquent lines may 

 be traced the rhythm of the myriad amoebiform animals which con- 

 structed the noble edifice when they sang together.^ The poesy 

 (TToa/o-is, iwiesis, a making) of the subject has been translated with 

 conspicuous zeal and success by Mi\ W. K. Parker ; its zoological 

 moral has been similarly pointed by Professor Huxley ; and the 

 young ornithologist who would not be hopelessly unfashionable 

 must be able to whistle some bars of the cranial song — the pterygo- 

 palatine bar at least. 



The rapid progress of ossification soon obliterates most of the 

 original landmarks of the skull, fusing the distinct territories of 

 bone in one great indistinguishable area. Thus the brain-box of 

 almost any mature bird is apparently a single solid bone, and most 

 parts of the jaw-scaffolding similarly run together. Aside from the 

 bones of the tongue, which are collectively separate from those of 

 the skull proper ; and of the compound lower jaw, which is freely 

 articulated with' the rest of the skull ; only two or three other 

 bones of the skull, as a rule, are permanently and perfectly free at 

 both ends. These are the quadrate bones — the anvil-shaped pieces 

 by which the lower jaw is slung to the skull ; the pterygoids, arti- 

 culating the palate with the quadrate ; and sometimes the vomer. 

 Traces only of distinctness among bones of the face and jaws are 

 usually found ; but even such vestiges disappear, as a rule, from 

 among the bones of the brain-box. It is necessary to any intelligent 

 understanding of the construction of a bird's skull, to learn some- 

 what of its mode of development in the embryonic stage ; this being 

 the only clue to the individual bones of which it is composed, and 

 so to any correct idea of its morphology. One theory is, that the 

 skull consists of four modified vertebrae ; and the principal bones 

 have been named and described by some writers in terms indicating 

 the elements of a theoretical vertebra. It is true that the skull is 

 segmented, or may be segmented off, like a chain of several vertebrae; 

 that it continues the vertebral axis forward ; that it has a lam 

 cranii like a series of vertebral centrums ; above which rises a seg- 

 mented neural arch enclosing the great nervous mass, and below 

 which depends a set of bones enclosing visceral parts like a haemal 



^ Bone-tissue chiefly consists of the aggregated skeletons of Osteamccbce — a kind 

 of iinicellular protozoan animals which inhabit in myriads the bodies of nearly all 

 the Vertebrata, possessing the faculty of feeding wpon phosphate of lime and other 

 earthy matters they find in the blood, and afterward excreting them in the form of 

 multiradiate exoskeletons of their own, collectively forming the whole skeleton of 

 their host. 



