GENERALITIES OF THE GAITS. 493 



Let us represent, for example, the running of a man by using the tracing of 

 this gait, as it was obtained by M. Marey (Fig. 186). 



The continuous line, D, corresponds to the curve furnished by the contacts of the right foot ; 

 the interrupted line, O, to that of the contacts of the left foot. The registering surface presents only 

 two horizontal lines, 1 and 2, since here only two members are in question. 



FIG. 186. 



This being said, let us draw a perpendicular, a, upon the plane, beginning at the point where 

 the curve of the right foot ascends ; this indicates the commencement of the contact of this foot. 

 Draw another perpendicular, b, from the point where this curve descends, which shows when the 

 foot is raised from the ground. Now let us join the bases of the two perpendiculars by a heavy 

 white line; this line, ab, will evidently have a length proportional to the duration of the contact 

 of the right foot. 



By making a similar diagram with the curve of the left foot, we will obtain the same rota- 

 tion for its contacts. The same operation is practised upon succeeding curves of the right or the 

 left foot. 



The intervals between the white lines correspond to the duration of the elevations of the 

 right foot ; those between the gray indicate the elevations of the left. 



As to the intervals comprised between the gray and the white lines, during which each 

 member is raised, they represent the duration of the periods of suspension of the body. 



This notation, applied to the horse, is equally simple. The only difference 

 is that the registering plane contains four lines instead of two, because the 

 phases of four members are to be noted. 



Duges ! has very appropriately compared the walking quadruped to two men 

 walking and placed one in front of the other : the one in front corresponds to the 

 anterior biped, the one behind to the posterior. Hence the notation of the gaits 

 of the quadruped should be similar to that which the two men furnish, if they 

 walk with the same rhythm and make the same number of steps. In order to 

 establish this, it will suffice to superpose the notations of the one in front to those 

 of the one behind, keeping in view the proper rhythm and the relations whi-ch 

 will exist between the movements of the one and the other. 



Let us select, for example, the amble, a gait in which, says M. Marey, 2 the two pedestrians 

 (anterior and posterior), going at a waljc, both execute the same movements with perfect con- 

 cordance. It is apparent that the notation will furnish us that in Fig. 187, whence it is proved 

 that the beats of the right foot and those of the left foot, produced in the same time by the man 

 in front and the one behind, are recorded by similar lines exactly superposed and of equal 

 length. 



1 Duges, Traite de physiologic compared de 1'homme et des animaux, t. ii. pp. 170 and 174, 

 Montpellier, 1838. 



2 Marey, loc. cit.. p. 146. 



