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MANUAL OF ELEMENTARY ZOOLOGY 



FlG. 302. — A pigeon opened from the ventral side to show the principal 

 organs in their natural positions. 



aj/i.s. t Anterior thoracic air sac; ii/'.s., abdominal air sac; ao.a.,, aortic arch; 

 6>\a., brachial artery; e.c, common carotid artery; c/.o., cloacal opening; 

 rr., crop ; dm., duodenum ; inn,, innominate arteries ; /., lung ; /?-., left 

 ventricle; /r., liver; ww., muscles concerned in the movements of (he syrinx; 

 ws., oesophagus ;/.w., pectoral is major muscle ; f'.t/t.s., posterior thoracic air sac ; 

 pan., pericardium (torniopen) ; f>cs., pancreas ; fic/.a., pectoral artery; r.v., 

 right ventricle; scl.il,, subclavian artery; thm., thymus; tra. t trachea. The 

 gizzard is seen opposite (he forceps which hold back the abdominal wall. 



