60 MATERIALS FOR A MEMOIR ON 



So far as the photographs in the Muybridge series are concerned 

 the order of succession of foot-falls could have been improved — 

 that is to say, could have been more accurate — if the movements 

 in the record of each gait had been of exactly the same character. 

 But in point of fact, owing to the practical difficulties surround- 

 ing the subject, scarcely any two of the series begin and end in the 

 same manner, nor has anything been recorded of the mental con- 

 ditions of the animal, whether it was tractable or intractable, 

 whether excited or quiet, etc., — conditions so essential to the 

 manner in which an animal may determine its motions. 



If it can be conceived that a perfectly tractable and composed 

 animal had been moving in a circle, and the camerse instead of 

 being arranged in a line had been grouped in a central cluster in 

 such a manner that they could secure correct pictures of the 

 moving form in the same way as in the method actually adopted, 

 it is likely that out of such an endless series a uniform set of 

 pictures might have been secured which would have given com- 

 pleteness of representative actions. It is reasonable to suppose, 

 that the motion of a living creature, as in an unvital mechanism, 

 when starting and when halting, may be different, and may present 

 contrasts of the several parts to a greater degree than when studied 

 at a regularly maintained rate, whether this be a high or a low 

 one. 



Each position of the foot when three feet are down embraces 

 the laterals with one of the opposed feet in addition. Thus, in 

 series 738, Fig. 1, in addition to the right laterals the left hind 

 leg is on the ground. But in none of the pictures were the left 

 laterals detected in which the right hind limb was "on." It is 

 probable that the diagonal heterochiral grouping is a weaker form 

 of support than the lateral, and is used as an expedient to shift 

 the laterals from the right to left and back. 



In the use of the laterals, in all gaits the feet as they approach 

 the end of the time at which they are " on" are at the side of the 

 trunk, while the feet in use as diagonals always remain beneath 

 the trunk. 



The facts that no variety of the deer ever paces, that the mule- 

 deer is the only variety that bounds, — i.e., that all the feet leave 

 and strike the ground together, — that the Canadian deer soon 

 becomes fatigued in the run, while this gait is the one longest 



