SKELETON 51 



behind tlie junction there are only two little vertebrsB 

 to represent the tail bones. Note also that the for- 

 ward end of this bony rod (called the wrostyU) has on 

 each side a projection against which the bones to which 

 the legs are fastened join directly. This really makes 

 three stiff rods side by side in the back here to resist 



Fig. 23.— Skeleton of frog. 



the sudden thrust of the powerful hind legs. Many^ 

 creatures leap, but none have themselves hurled for- 

 ward by a stroke directly at the rear end of the spinal 

 column, as the frogs. These projecting pieces at the , 

 forward end of the rod are called " the transverse 

 processes of the sacral vertebrae," and may or may 

 not be more or less expanded at their outer ends, 



