402 WORK OF THE PHYSIOLOGICAL STATION AT PARIS. 



Not only does cbrono-pliotogTaphy afford a means of studying the 

 kinematics of movements, it also funiisbes an indication of the work 

 performed in certain muscular acts. 



A distinguished engineer, M. Fremont, has just made at the physio- 

 logical station a study of the Avork performed in hammering iron upon 

 an anvil. On a movable film M. Fremont took the .series of attitudes 

 assumed by the blacksmith in the successive movements given to the 

 hammer.' By chronophotography on a fixed plate there Avas shown 

 tbe trajectory of the hammer and its successive positions at definite 

 instants, the intervals between which weremeasured bj- a chronographic 

 dial. 



By such a figure we can estimate the forces acting upon the mass of 

 the hammer at each instant by means of the acceleration given to that 

 mass. AVe also obtain a measure of the work, since it shows tlie 

 velocity of the hammer at tbe moment it is about to strike the iron. 



In most physiological acts forces and work should be measured by 

 another method — that is to say, by the dynamograpb. I have described 

 under the name of dynamographs certain instruments that show the 

 forces of i^ressure or traction applied to them by me.ms of a stylus that 

 traces tbe curve of variations of these forces.- I bave also shown bow 

 the results obtained from these instruments may be synchronized with 

 those obtained from chrono-pbotography, so that we may know at each 

 libase of a footfall, for example, what force tbe foot exerts upon tbe soil 

 in a vertical direction. If a traction dynamograpb indicates the force 

 developed by the same act, we may by combining these different data 

 obtain all tbe information necessary to understand tbe mechanism of 

 locomotion in different animals. 



The number of experiments necessary may seem to you excessive, 

 but tbe invention of methods, tbe care required to secure their preci- 

 sion, their first application to the analysis of movements and to the 

 measure of forces constituted the most arduous part of the task. 

 Already our records accumulate; the field of jiossible comparisons 

 enlarges every day, and at the same time tbe interest in anatomo- 

 physiological comparisons increases. I wish to give you some examples 

 of these comparisons. 



IV. 



If we wish to study locomotion in different types of mammals so as 

 to elucidate the variety of their forms by tbe special movements char- 

 acteristic of each we must first ascertain all the anatomical and physi- 

 ological elements necessary for such a comparison. 



Drawings and plates will not suffice as anatomical material. It is 

 necessary to use natural organs, skeletons, articulations, preparations, 

 or casts of muscles. Now, thanks to the ready assistance of various 



' These studies will shortly l>e published by M. Fri5iuont. 

 " See Le Mouvemeut, page 142. 



