10 MOVEMENT 



ground compresses the balls with which they are pro- 

 vided, and forces the contained air into the recording 

 tambours. The method tallies in all respects with 

 that employed in the case of man. However, on 

 account of the multiplication of writing needles, which 

 the greater number of footfalls necessitates, the four 

 needles are grouped in two series, one to record the 

 movements of the fore feet, and the other placed 

 beneath it to record the steps of the hind feet. In 

 both series, the white lines indicate the movements of 

 the right feet, while diagonally shaded ones represent 

 those of the left. 



Fig. 8 shows results obtained in this way of the 

 three ordinary paces, namely, ambling, walking, and 

 trotting.* It will be noticed that each record is repre- 

 sented as a series of four tracings, such as would be 

 obtained by arranging in parallel series the tracings 

 of two men walking. In fact, a quadruped may be 

 compared to two bipeds — to two men, for instance — 

 walking one behind the other, one to represent the 

 fore, and the other the hind limbs. Such a pair 

 would take the same number of steps ; but the phases 

 of rest and motion would assume different relations 

 in the two cases. 'It is this which constitutes the 

 difference between the various kinds of paces. For 

 instance, when the corresponding hind and fore feet 

 move simultaneously, the horse is ambling (Tig. 8, first 

 record). If the right fore foot is in the mid phase 

 of rest when the left hind foot reaches the ground, 

 the horse is walking (second record). Lastly, if the 

 anterior and posterior legs move in opposite pairs, 

 i.e. if the anterior right reaches the ground at the 



* It is more than twenty-one years ago that these experiments were 

 made, and we remember with gratitude the patient assistance with 

 which Messrs P.. llier and Gabriel Pail lard helped us to carry them 

 into effect. 



