THE ANATOMY OF BIRDS. — OSTEOLOGY. 155 



The Pubis (Lat. pubis, bone of the front of the liuman pelvis where the hair grows at 

 puberty ; pi. puhes ; adj. 2}ubic; figs. 56, 60, 61 P), beginning at its share of the acetabular ring, 

 is a long slender bone which runs ahjng the lower border of the ischium, sometimes for a short 

 distance only, often for the whole length of the ischium, and usually projecting behind ; more 

 iir less perfectly parallel with, applied to, or united with, the inferior ischiac border. When 

 separate, a long deep fissure results ; when united at the end, a long narrow foramen is 

 formed ; when incompletely united in any part of its ischiac continuity, a fissure and a foramen, 

 in the ostrich two foramina, result. All these conditions occur ; in any case, such ischio-pubic 

 interval corresponds to the obturator foramen (fig. 56, o; fig. 60, ob) of human anatomy ; it is 

 greatest in Cretaceous birds and existing Batitce. The free ends of the pubes may be more or 

 less expanded. In the ostrich only there is a pubic symjihysis of the ends of the bones ; in the 

 same bird a separate ossicle, situated upon the lower border of the pubes, and called epipubic, 

 is considered to represent a " marsupial " bone (Garrod). In various birds, among them our 

 ground cuckoo, Geococcyx californianus, the pubis projects a little forward, under the ace- 

 tabulum : this prominence is the propubis. Separation of the pubes is supj^osed to be for 

 amplification of the pelvic strait to facilitate the passage of the large chalky eggs birds lay. 



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 rhythmic rhymes of the myriad 

 ainoebiform animals which constructed the noble edifice when they sang together.^ The poesy 

 (noiriais, poiesis, a making) of the subject has been translated with conspicuous zeal and success 

 by Mr. 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 

 l)rain-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 collec- 

 tively separate from those of the skull proper ; and of the compound lower jaw, wliich 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, articulating the palate with 

 the quadrate ; and sometimes the vomer. Traces only of the bones of the face and jaws are 

 usually fnuud ; 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 somewhat 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 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 basis cranii like a series of 

 vertebral centrums, above which rises a segmented neural arch enclosing the great nervous 

 mass, and below which depends a set of bones enclosing visceral parts like a hannal arch. 

 The hindmost cranial segment, the occipital bone, resembles a vertebra in many physical 

 diaracters, and even in mode of development. But if the serial homology of the skull with 



' Boi.e-tissue chiefly consists of tlie aggregated skeletons of Osteamabce — a kind of uni-cellular protozoan 

 animals wliicli inhabit in myriads the bodies of nearly all the Vertcbrata, possessing the faculty of feeding upon 

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

 miiltiradiate exoskeletons of their own, collectively forming the whole skeleton of their host. 



