ISOLATED EFFECTS OF BEAUTIFUL PROPORTIONS. 407 



B. Conditions of the Motor en Mode de Vitesse, or of 



Velocity, Speed. 



We include in the category of motors suited especially for speed 

 all saddle-horses, carriage-horses, and light draught-horses, whose 

 habitual gait is the trot or the gallop. Here the object to be ac- 

 complished consists in the distance which the animal, burdenedTwith a 

 slight weight, is capable of travelling during a unit of time. As to 

 the quantity of movement, mv, it remains the same as in the case of 

 working by the weight of the mass, only the factor ra, mass, is reduced 

 as much as possible, while the factor v, velocity, which we wish espe- 

 cially to utilize, is thereby correspondingly increased. 



Now, the rapid moving of the centre of gravity over the surface of 

 the soil is absolutely dependent upon the two following conditions : 



1st. The length of the strides. 



2d. The number of strides taken during a unit of time. 



The extent of each step is itself the consequence of several second- 

 ary mechanical dispositions already known, and upon which it would 

 be useless to insist. It is, primarily, the absolute length of the columns 

 of locomotion which renders them more apt to span over much ground ; 

 it is, secondarily, the considerable length of the muscles belonging to 

 the superior regions of these columns and commanding their dis- 

 placements ; finally, it is the particular orientation of the articular 

 angles, permitting the osseous segments to pass more freely over the 

 space in the direction of the movement without losing force in raising 

 the body. 



As to the number of steps, it depends exclusively upon the rapidity 

 of the muscular contractions, that is to say, upon the energy pos- 

 sessed by the animal, upon the intensity of his nervous stimulation, 

 and upon the time during which he can renew them. 



But one feature which it is important to take into consideration 

 when speaking of the conformation of fast motors, is the light weight 

 of the body. M. Sanson l says that " beyond a certain weight they 

 can no longer be utilizable, since the strength which they dispose of is 

 just sufficient to move their own mass about. ... It is, then, no wonder 

 that the heavy French cavalry horse has never been able to endure 

 the hardships of a campaign if at all prolonged, and that even when 

 in garrison their mortality is 50.57 per thousand, whilst that of the 

 light cavalry horse is only 23.33. . . . The smaller and lighter saddle- 



1 A. Sanson, Traite de zootechnie, t. iii. p. 330, et suiv. 



