4 THE EXTERIOR OF THE HORSE. 



at each instant are displaced in different directions, and thus are modified the 

 weight and volume of the organs in which the molecular changes take place. 

 Other displacements, much more considerable, indeed even more important from 

 the point of view which concerns us, are due to the actions of the organs, the 

 different attitudes of the body, or the movements which are caused by locomo- 

 tion. We understand, then, how. difficult becomes the exact determination of 

 the centre of gravity, and the great importance of sufficiently appreciating its 



FIG. 1. Situation of the centre of gravity in the horse. 



displacements when it is a question of obtaining from it the conditions of equi- 

 librium. 



According to Borelli, 1 the centre of gravity in the horse is situated in the 

 middle of the height of the trunk, and the line of gravitation falls through the 

 centre of the quadrilateral formed by the four members. 



According to Professor Colin, 2 it almost corresponds to the intersection of 

 two lines, one of them (vertical) passing back of the xiphoid appendix of the 

 sternum, the other (horizontal) separating the middle from the inferior third of 



1 Borelli, De motu animalium, Naples, 1734. p. 126. 



8 G. Colin, Trait6 de physiologic comparee des animaux, 3e edition, Paris, 1886, t. i. p. 460. 



