The Framework of the Bird 



17 



hence the separate bones which unite it to the vertebrae 

 of the lower back. The evolution of the tail will be 

 treated of in another chapter. 



Ribs 



The ribs are the long, narrow, double-headed bones 

 which curve out from the vertebrae of the upper back 

 and, uniting with the breast-bone, form a barred pro- 

 tection for the heart, lungs, 

 liver, and other organs. These 

 are the ribs proper, but there 

 are other smaller ones, called 

 false or floating ribs, which 

 reach only part of the way 

 around the body. Look at 

 the largest ribs of the chicken 

 and an added provision for 

 making this box of bone more 

 solid wull be seen. From near 

 the centre of the upper part 

 of each rib a small bony projection laps across the rib 

 next behind and thus forms a kind of lattice-work, 

 movable but of great strength. A further interest 

 attaches to these cross-rib pieces when we learn that every 

 bird except the Screamer possesses them, while else- 

 where they are found only in crocodile-like reptiles 

 and in the Hatteria Lizard of New Zealand. 



The similarity of the ribs— slanting one after another 



Fig. 56. — Ribs of Hatteria Lizard, 

 with uncinate processes. 



