AVES 



rudder, ailerons, stabilizers. Let us consider the ways in which the 

 bird meets these requirements. 



1. Planes or Wings. The wing of the bird (Fig. 142) is a complex 

 of several structural elements consisting of: a framework of bones, 



Anatomy of the pigeon. A, nostril; AD, ad-digital primary feather; 



uditory meatus; BW, bastard wing; C, oesophagus; CA, right carotid 



J, crop; DA, aorta; E, keel of sternum; F, right auricle; G, right ventricle; 



aepatic vein; HI, left bile-duct; H2, right bile-duct; /, distal end of stomach; 



. .., right innominate artery; IV, posterior vena cava; JA, left innominate artery; 



JV, right jugular vein; K, gizzard; L, liver; M, duodenum; MD, mid-digital 



primary feathers; MP, metacarpal primaries; Ml, preaxial metacarpal; M2, 



middle metacarpal; MS, postaxial metaearpal; N, cloacal aperture; Nl, preaxial 



digit; O, bursa Fabricii; 01, proximal phalanx of middle digit; O2, distal phalanx 



of middle digit; P, pancreas; PA, right pectoral artery; PD, predigital primary; 



PV, portal vein; PI, first pancreatic duct; P2, second pancreatic duct; PS, third 



pancreatic duct; O, pygostyle; R, rectum; RC, radial carpal bone; RX, rectrices; 



Rl, ulnar digit; S, ureter; SA, right sub-clavian artery; SV, right anterior vena 



cava; T, rectal diverticulum; U, kidney; UC, 'ulnar carpal bone; V, pelvis; 



W, lung; X, humerus; Y, radius; Z, ulna. (From Hegner, after Marshall 



and Hurst.) 



muscles, nerves, blood vessels, and feathers. The bony framework is 

 that of a modified fore limb of which the human arm is a good proto- 

 type. *The humerus is large ^ has heavy ridges for the attachment 

 of the huge pectoral flight v ' a \Uature ; ' The radius and ulna are 

 largely unmodified, thoug v ' ne ston x is larger than the radius and has 



