THE FORERUNNERS OF THE HORSE 279 



All these changes culminate in producing not 

 only a strong and yet graceful type of limb, moving 

 rapidly in the same fashion as a short pendulum, 

 and thus combining rapid movement with a long 

 stride, but they also cause the centre of gravity of 

 the body to be raised high above the ground, which 

 is likewise a mechanical advantage in galloping. 



"The pendulum-like motion of the limbs," 

 writes Dr. Lull, " being all in one plane, the joints 

 become pulley-like through the formation of inter- 

 locking tongues and grooves, which effectually 

 limit any lateral motion. There is also a reduction 

 of the ulna in the fore-arm and of the fibula in the 

 lower leg, as these bones, especially the former, are 

 associated with more varied movement. 



" In this evolution the hind-foot is the more pro- ,^ 

 gressive, as the fore-limb retains its general utility 

 for a longer time. Finally, however, after vast 

 ages, the fore-foot overtakes the hind, and thence-^" 

 forth the degree of evolution in each is the same. 

 Still, it is curious to note that, among living horses, 

 in instances of reversion to ancestral conditions the 

 fore-foot is more apt to exhibit well-developed 

 atavistic toes, showing that in it the reminiscent 

 tendencies are stronger." 



As regards the evolution of the teeth. Dr. Lull 

 has summarised the case so graphically that his 

 own words may once more be quoted in full : — 



" In the evolution of the teeth," he writes, "we 



