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COLLEGE ZOOLOGY 



trunk. The head is prolonged in front into a pointed, horny 

 beak, at the base of which is a patch of naked, swollen skin, 

 the cere. Between the beak and the cere are the two oblique, 



AD 



FIG. 471. Anatomy of the pigeon. A, nostril; AD, ad-digital primary 

 feather; B, external auditory meatus; BW, bastard wing; C, oesophagus; 

 CA, right carotid artery; D, crop; DA, aorta; E, keel of sternum; F, right 

 auricle; G, right ventricle; HV, hepatic vein; Hi, left bile-duct; H2, right 

 bile-duct; /, distal end of stomach; IA, 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; Mi, preaxial metacarpal; M 2, middle metacarpal; MS, postaxial 

 metacarpal ; N, cloacal aperture ; Ni, preaxial digit ; O, bursa Fabricii, 

 Oi, proximal phalanx of middle digit; 02, distal phalanx of middle digit; 

 P, pancreas; PA, right pectoral artery; PD, predigital primary; PV, portal 

 vein; Pi, first pancreatic duct; Pz, second pancreatic duct; PS, third pancre- 

 atic duct; Q, pygostyle; R, rectum; RC, radial carpal bone; RX, rectrices; 

 Ri, ulnar digit; 5, ureter; SA, right subclavian 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 Marshall and Hurst.) 



slit-like nostrils (Fig. 471, A). On either side is an eye which 

 is provided with upper and lower lids, and with a well-developed 

 third eyelid, or nictitating membrane. The third eyelid can be 



