622 



AVES 



[CH. 



12 



FIG. 312. The chief viscera of the Pigeon, Columba livia x f . 



1. Trachea. 2. Thymus gland. 3. Oesophagus. 4. Crop. 5. Syrinx. 



6. Heart. 7. Liver. 8. Gizzard. 9. Duodenum. 10. Pancreas. 



11. Small intestine. 12. Rectum. 13. Cloaca. 14. Air-sacs. 



15. Left carotid. 16. Left subclavian. 17. Right carotid. 18. Brachial 



artery. 19. Eight subclavian. 20. Muscles of syrinx. 21. Pector- 

 alis major muscle cut across. 



