340 



PRACTICAL ZOOLOGY 



curved claws for capturing their prey. Birds that spend most 

 of their time in flight, like the swift, possess weak feet. Usually 



01 Rl BW 



MO 



FIG. 217. 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 ; I, 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 ; Ml, preaxial metacarpal ; 

 M2, middle metacarpal ; M3, postaxial metacarpal ; N, cloacal aperture ; 

 Nl, preaxial digit; O, bursa Fabricii ; Ol, 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; P3, third pancreatic duct; Q, 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 Marshall and Hurst.) 



there is one toe behind and three in front, but in many wood- 

 peckers there are two in front and two behind, an arrangement 

 which doubtless enables them to cling to the bark of trees more 



