THE GAITS IN PARTICULAR. 547 



which form the second period of contact, and which are interposed 

 between the other two lateral disassociated beats. In opposition to the 

 preceding, we propose to call this gallop lateral. It has been for a 

 long time known to veterinarians as the disunited gallop. The horse 

 executes it rarely and with dijficulfi/, for this quadruped uses especially 

 diagonal gaits. Other animals, such as the dog, practise it ratiier fre- 

 quently, and we should not be surprised if the dromedary and the 

 giraffe, which take so easily the lateral type of locomotion, use it 

 without difficulty under certain circumstances. 



Be this as it may, the term disunited suits well for the lateral 

 gallop, because it expresses the defect in the harmony of the move- 

 ments of the two bipeds. 



As long as the horse progresses at the lateral gallop upon a 

 straight line, it is not necessary to employ a special expression to 

 characterize his gait ; the word disunited suffices. If, on the contrary, 

 he describes a curvilinear trail, it is called disunited in front when, 

 moving towards the left, for example, his anterior biped gallops to the 

 right (Fig. 237, A), and disunited behind when his posterior biped 

 does not gallop to the left (Fig. 237, B). 



Definition of the Normal Gallop of the Horse. — We now 

 possess all the elements necessary to an understanding of the defini- 

 tion of the normal (diagonal) gallop, the only one with Avhich we will 

 hereafter occupy ourselves. 



It is a fast, leaped gait, with three times, in which the simultaneous 

 beats of a diagonal biped occur between the two successive beats of the 

 opposite diagonal biped which commences the stride with the corre- 

 sponding posterior member. 



Each stride is separated from the following by an interval of time 

 called projection, during which the body is in the air. 



Kinematic Analysis of the Play of the Members.— Messrs. Marey 

 and Pages ^ rightly attribute, in the gallop, a different role to the posterior mem- 

 bers. The one which touches the ground first, receiving the entire body, consti- 

 tutes a powerful agent of dispersion at the beginning of its contact, while the 

 other fulfils the oflice of a propelling agent. 



This remark being made, let us see the relative peculiarities of the articular 

 trajectories. 



1st. Anterior Member (Fig. 238).— J. Phase of Contact.— The articular 

 trajectories are very analogous to those of the trot in the inflection of the curves 

 during the period of dispersion, but their rising is more marked on account of 

 the more intense fall of the body and the greater elongation of the member at 

 the end of this phase. 



' Marey et Pag6s, Mouvement du membre post^rieur, note communiqu^e. 



