AVES 



261 



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 comple.x 

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



HO MP PD 03 



Fig. 142. — Anatomy of the pigeon. A, nostril; AD, ad-digital primary feather; 

 B, e.xternal auditory meatus; BW, bastard wing; C, cesopliagus; CA, riglit carotid 

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

 HV, hepatic vein; HI, left l^ile-duct; HS, right bile-duct; /, distal end of stomach; 

 I A, right innominate artery; IV, posterior vena cava; J A, left innominate artery; 

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

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

 middle metacarpal; MS, postaxial metacarpal; A'', cloacal aperture; Nl, preaxial 

 digit; 0, bursa Fabricii; 01, proximal phalanx of middle digit; 03, distal phalanx 

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

 PV, portal vein; Pi, first pancreatic duct; Pi, second pancreatic duct; P3, 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 and has heavy ridges for the attachment 

 of the huge pectoral flight musculature. The radius and ulna are 

 largely unmodified, though the ulna is larger than the radius and has 



