The Framework of the Bird 77 
id 
hence the separate bones which unite it to the vertebrz 
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 vertebre 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 will be seen. From near  F'6. 56.—Ribs of Hatteria Lizard, 
with uncinate processes. 
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 
