IKRITABILITY 



107 



Fie. 64.-The ribs of the left side, with the dorsal and two lumbar vertebrae, the 

 rib cartilages and the sternum. (From Martin.) 



into an upper part, consisting of a single large bone, and 

 a lower part, consisting of two bones placed side by side 

 that turn on each other. A number of small bones con- 



