14 ZOOPRAXOGRAPHY 



each of the 3 next plates, and so forth until each series 

 of exposures in each of the three batteries is completed. 

 Assuming the operator to have exercised good judg- 

 ment in regulating the speed of the apparatus, and in 

 making the first electric contact at the proper time, 

 and that the figures 1 to 12 represent the distance 

 • traversed by the model in executing the movement 

 desired, the first three photographic exposures — that 

 is, one exposure in each battery — will have been syn- 

 chronously made when the model was passing the 

 position marked '' 1 " on the track T; the second three 

 exposures will have been made when the model was 

 passing the position marked ^"2," and so on until 

 twelve successive exposures were simultaneously made 

 in each of the three batteries. This perfect uni- 

 formity of time, speed, and distance, however, was not 

 always obtained. 



When this monograph was commenced it was not 

 intended by the author to give any more than a general 

 idea of the method adopted for obtaining the results of 

 his investigation; it has, however, been considered that 

 a few illustrations and brief description of the appa- 

 ratus devised and used by him may not be without in- 

 terest to other students. 



For the use of these illustrations he is indebted to 

 the courtesy of Rev. Jesse Y. Burk, the Secretary of 

 the University, and to J. B. Lippincott Company, the 

 publishers of ''The Muybridge Work at the Univer- 

 sity of Pennsylvania," a book which contains, among 

 other essays upon the subject, "Materials for a 

 Memoir on Animal Locomotion, by Harrison Allen, 

 M. D.," and " A Study of Some Normal and 



