THE ANATOMY OF BIBDS. — OSTEOLOGY. 



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The Clavicles, or Furculum (Lat. clavicula, a little key : furciilum, a little fork ^ 

 figs. 56, 59, c7), or the clavicular arch, are the pair of bones which when united together form 

 the object well known as the " merry-thought" or *' wish-bone," corresponding to the human 

 " collar-bones." They lie in front of the breast, across the middle Hue of the body like a V 

 or U ; the upper ends uniting as a rule both with scapula and coracoid. For this purpose, in 

 most birds, the ends are expanded mt)re or less ; such expansion is called the epicleidium (Gr. 

 (ni, epi, upon ; Kkeiblov, kleidion, the collar-bone) ; in Passerine birds it is said to ossify separ- 

 ately, and is considered by Parker to represent the procoracoid of reptiles. At the point of 

 union below, the bones often develop a j)rocess (well shown in the domestic fowl) called the hypo- 

 cleidium (Gr. viro, hypo, under ; fig. 59, lie), supposed to represent the interclavicle of reptiles. 

 The clavicles are as a rule present, perfect, anchylosed together, articulated at the shoulder; in a 

 few birds anchylosed there; in several, there and 

 with the keel of the sternum ; in Opisthocomus there 

 aud with the manubrium of the sternum. In various 

 birds, chiefly Picarian and Psittacine, they are de- 

 fective, not meeting each other. They are wanting 

 in Struthio, Rhea, Apteryx, and some Psittaddce. 

 Besides curving toward each other, the clavicles 

 have usually a fore-and-aft curvature, convex for- 

 ward. In general, the strength of the clavicles, 

 the firmness of their connections, and the openness 

 of the V or U, are indications of the volitorial or 

 natatorial power of the wings. The end of the fur- 

 culum is hollowed for a fold of the windpipe in the 

 crested pintado (Owen). 



4. THE PELVIC ARCH. 



The Pelvis (Lat. pelvis, a basin, fig. 60), is 

 that posterior part of the trunk which receives the 

 uro-genital, and lower portion of the digestive, vis- 

 cera. It consists of the "sacral" vertebrae on the 

 middle dorsal line, flanked on each side by the bones 

 of the pelvic arch, which supports the hind limb. 

 In vertebrates generally the pelvic basin is com- 

 ])leted on the ventral aspect by union (symphysis ; 

 Gr. avv, sun, together ; ^vais, growth) of the bones 

 from o{)posite sides. Excepting only Struthio, which 

 has a pubic symphysis ; and Bhea, which has an 

 ischiac symphysis just below the sacral vertebra", 

 the pelvis of a bird is entirely open below and 

 behind ; each pelvic arch anchylosing firmly with 

 the sacral vertel)r{e to form a roof over the viscera 

 above named. This sacro-iliac anchylosis is com- 

 monly coextensive with th(! confluence of the many 

 vertebrte whicli make the "sacrum" of ordinary 

 language, that is, fn.m the first dorso-luml)ar to the 

 last uro-sacral. The whole roof-like affiiir l(M)ks 

 something like a keelless stenium inverted. The 

 pelvic arch of each side consists of three bones, ilium, 



P'iG. 60. — Telvis of a heron {Jrdcn Iterodins), 

 nat. size, viewed from below; from nature by Dr. 

 R. W. Sliufeldt, U.S.A. (I/, dorso-lumliar vertebrae 

 to and including the last one, sc ; below sc, for the 

 extent of tli«/ffr(7<'black8i)aces(oi)positetliearrow) 

 are the true sacral vertebr.-E; h.s', nrosacral verte- 

 brae (opposite the five oval black spaces ; //, ilium ; 

 /s, ischium; /', pubis; nl>, obturator foramen. 

 The arrow flies into the acetabulum. 



