626 



AVES 



[CH. 



and give rise to tufts of tubes. The ventral ducts disappear, the 

 tufts of tubes which were connected with them acquire secondary 

 connections with the dorsal tuft whose duct now serves to discharge 

 the products of all three tufts and which persists as the adult 

 pancreatic duct. In Birds, however, all the three pancreatic ducts 

 appear to persist. The intestine is folded into four or five loops, 



15 



FIG. 313. The lungs, kidneys and gonads of a Pigeon, Columba lima x-f. 



1. Trachea. 2. Bronchus. 3. Lung. 4. Suprarenal body. 5. Ovary. 

 6. Oviduct. 7. Lobes of kidney. 8. Ureter. 9. Aorta. 10. Bursa 

 Fabricii. 11. Kectum. 12. Opening of bursa Fabricii. 13. Openings 

 of ureters. 14. Opening of oviduct. 15. Cut pectoral muscle. 



the arrangement of which has been made use of as a basis for 

 classification. It ends by passing into a short rectum or large 

 intestine, which is marked by a pair of out-growths, the intestinal 

 caeca. Their size varies much, from long and wide blind sacs, as 

 for instance in the Common Fowl, Ducks, Geese and other herbivorous 

 birds, to quite small vestiges as in the Pigeon and in fish- and flesh- 

 eating birds. The rectum ends in an enlargement termed the 



