ANIMAT. LOCOMOTION. 61 



assumed by the Virginia deer,* point to the conclusion that 

 natural gaits are correlative with structural peculiarities; and 

 while quadrupedal movements are based on the same plan, they 

 are subject to modifications in animals otherwise closely related. 



Gait may be modified, if not controlled, by the proportion of 

 the length of the limbs to the trunk. The hippopotamus walks 

 in perfect synchrony, so far as the unaided eye cari detect. The 

 fat pig can walk, but cannot gallop. The lean pig, on the other 

 hand, can gallop. 



The fact that the giraffe is the only animal which is a pacer for 

 both slow and fast movements cannot be easily disassociated from 

 the great length of the limbs. 



The subject of the gait can be studied by observation of the 

 animal as a whole, by numerical analysis of each foot as it is 

 either " on" or '' off" the ground, by numerical analysis of each 

 combination of any number of feet, and by graphic analysis, by 

 which means tracings of the feet in combination are secured. 



For convenience the subject is divided into the following heads : 



The Synchiral Gaits. 



The Heterochiral Gaits. 



Synchiral Gaits. 



The Synchiral gaits embrace the canter, the gallop, and the run. 



In the canter the momentum of the body is not sufficient to 

 enable both the fore limbs to act as props until the hind limbs 

 again are in the position to urge the body forward. Hence the 

 animal is observed to come down upon a fore limb after being in 

 the air. 



In the gallop the fore limbs act successively as props before the 

 hind limbs come down. The run is the variety in which the 

 limbs attain the greatest possible amount of strain, and in which 

 the quick succession of the paired feet is absolute. 



The "jump" is an incident in the run. In jumping a hurdle 

 the horse, in series 641, appears to come down on two fore feet at 

 the same moment. In series 637 the horse comes to the ground 

 on the left fore foot, and is instantly followed by the hind foot of 

 the same side. 



* J. D. Caton, The Antelope and Deer of America, p. 270. 



