In his foreword to a military handbook published in 1899, physiologist Etienne-Jules Marey deplored the incorrect ways of walking that he saw in everyday city life: "We are the slaves of conventional aesthetics, both in regard to walking and to all other processes of life. This is because we have been taught since our childhood that to have a distinguished gait one must hold the chest straight, not move one's arms, and turn one's foot outward with an extended knee when putting it on the ground. Aesthetics are everywhere. Did we not see that during the past century the equerries made it their ideal to assemble their horses for the purpose of inducing them to execute movements that were considered elegant? They even went so far as to ridicule the rider who seemed to demand nothing more of his horse than the quickest possible arrival at his destination." 1 The yoke of "ridiculous" conventions imposed by the dictates of fashion was to be shaken off by the physiologist, who entered the fray with an arsenal of new machines:Chronophotography, combined with the use of dynamometers, provides us with exact information about all of the acts we execute, which often reaches our consciousness in a very incomplete form. In this way it becomes the educator of our movements, allowing us to recognize the ideal perfection that we should attain and to recognize both our incorrect movements and the progress that we have made. Thanks to the progress of the graphical method, the mechanical act of locomotion can be translated into geometric curves, in which everything becomes measurable with a precision that mere observation could never attain. 2 According to this depiction of the duel between aesthetics and experimental science, it is inevitably the latter that emerges victorious. Science, after all, is 88 A B S T R A C T The late nineteenth-century debates about forms of dressage and the correct representations of horses, using the circus as the major arena for testing and observation, provided a fertile ground for the development of Etienne-Jules Marey's physiology of locomotion. Marey claimed to revolutionize the field of locomotion studies with mechanically produced representations, yet, as this essay shows, his mechanical reform of the study of bodies in motion was countered by the persistence of older forms of animal observation and superseded by new anthropologies and psychologies of seeing. / REPRESENTATIONS 111. Summer 2010