446 THE POPULAR SCIENCE MONTHLY. 



movement of the lever opposite to that described above. Thus the 

 lever records accurately every movement of the membrane of the dis- 

 tant drum, and the intervening flexible tube allows one to attach the 

 drum to the limb of a moving man, or quadruped, to the wing of a 

 flying-bird, or to the chest, to obtain the traces of the motions of the 

 lungs and of the heart. 



In 1863 Marey first began to apply the graphic method to biologi- 

 cal studies, in his " Physiologie medicale de la Circulation du Sang." 

 In 1868 he published his "Du Mouvement dans les Fonctions de la 

 Vie." In the preface of this truly valuable work he says: "By the 

 use of the graphic method the illusions of the observer, the tedious- 

 ness of descriptions, and the confusion of facts, disappear. These two 

 ruling qualities, clearness and conciseness, become every day more de- 

 sirable, by reason of the enormous increase in biological publications." 

 In his last work, " Animal Mechanism," be has illustrated this remark ; 

 for surely no " tediousness " will be experienced in the perusal of this 

 work, in which we are taught, with such " clearness and conciseness," 

 how men and quadrupeds walk and run, and how birds and insects fly. 



The desire to see Marey's work on Animal Mechanism fully appre- 

 ciated by the public has induced us to put the reader in possession of 

 his quite recent discoveries, which could not be incorporated in the 

 book published in the " International Series." We refer to two of his 

 most important researches, one on " Human Locomotion," taken from 

 the Comptes Rendus, of July 13, 1874 ; the other, " On the Resistance 

 of the Air under the Wing of a Bird during its Flight," we take from 

 the Journal de Physique of July, 1874. 



I. New Experiments on Human Locomotion. The brothers We- 

 ber believed that in human locomotion the oscillation of the leg in 

 walking was due alone to the action of gravity; this is to say, that the 

 foot, while off the ground, has the motion of a pendulum. For a long 

 time this opinion has held its place in physiology, but it has been op- 

 posed, in recent years, by arguments of various kinds. First, by M. 

 Duchenne, of Boulogne, who showed that the leg is not entirely passive 

 during its displacement, for certain muscular paralyses prevent its 

 oscillation ; M. Giraud-Teulon has attacked the theory of Weber, by 

 showing the mathematical errors on which it is founded ; and, finally, 

 M. Carlet has determined, experimentally, the active function of cer- 

 tain muscles in the displacement of the leg during walking. 



If gravity does not alone act in producing the oscillation of the leg, 

 it becomes impossible to foresee what motion will result from its com- 

 bination with muscular action. I have appealed to the graphic method 

 for the experimental answer to this question. 



When a body moves in a straight line, with variable velocities at 

 each instant, it is easy to obtain the graphic representation of its 

 motion, provided the space moved over is not too extensive. It 



