498 



NATURE 



\Oct. 2 2, 1874 



MAREY'S "ANIMAL MECHANISM'' 

 Animal Mechanism. By E. J. Marey. "The Inter- 

 national Scientific Series." (London : Henry S. King 

 and Co., 1874.) 



ON more than one occasion during the last year or so, 

 we have drawn attention to a small French physio- 

 logical treatise by Prof. Marey, entitled " La Machine 

 Animale." It is not only to a passage here and a passage 

 there that we have had to refer, but to the thorough exposi- 

 tion of intricate problems of mechanical physiology, which 

 have been worked out with a degree of ability rarely to 



be found in a single author. It is a translation of this 

 work which forms the subject of the present review. 



Prof. Marey divides his subject into three parts : the 

 first devoted to general principles ; the second to terres- 

 trial locomotion ; and the third to aerial locomotion. It 

 is to the last two of these that we wish to draw attention 

 both in this and the succeeding notice. 



Terrestrial locomotion comprises that of bipeds and 

 that of quadrupeds : man and the horse, exemplifying 

 them respectively in their most complicated forms, serve 

 as excellent examples. Human locomotion is a subject 

 which admits of more scientific treatment than might at 



first sight be supposed. There is no better proof of this 

 than the fact that until Prof. Marey quite recently dis- 

 proved it, the theory of the brothers Weber was generally 

 accepted, namely, that the non-supporting leg moves 

 pendulum-like in walking. 



Whilst, with the mind otherwise unoccupied, anyone 

 sets to work to study the different movements of his 

 legs in hopping, jumping, walking, and running, there 

 are many points that he can make out without further 

 assistance, such as the fact that in walking the feet are 

 never both off the ground together, whilst in running the 

 body is unsupported between each two steps. Our author 

 and one of his pupils, M. G. Carlet, have, however, suc- 

 ceeded in putting down the results of their carefully 

 conducted experiments in a form which allows of their 

 being studied by others as well as by the subjects of the 



experiments themselves. By means of elastic air-bags 

 with connecting tubes they have transferred the move- 

 ments they discuss to paper, and have had these tracings 

 copied as woodcuts. 



After having proved that the intensity of the pressure 

 of the foot upon the ground is not solely dependent on the 

 weight of the body, it being greater at the end of the 

 step than at its commencement on account of the mus- 

 cular effort then added, Prof. Marey describes the 

 vertical and horizontal movements of the body in walk- 

 ing, and shows that the former oscillations are twice as 

 numerous as the latter. This can be verified by obser- 

 vation ; at all events, the rise of the body can be seen to 

 be as rapid as each step, whilst the slowness of "the 

 waddle " is proverbial. Next, the greater pressure at the 

 end of each step is proved, by a very ingenious con- 



trivance, to increase the forward movement of the body 

 during that time, and to be least at the moment when the 

 foot reaches the ground. 



In describing the rhythm of the different modes of 

 progression adopted by man, the tracings obtained by 

 the recording instrument are transcribed into a notation 

 which is a modification of that employed in music. Two 

 horizontal lines form the staff on which this simple 

 music, consisting of only two notes, is written. A broad 

 white line expresses by its length the duration of the 

 pressure of the right foot ; a similar shaded line does 

 the same for the left ; any interval between the two 

 indicates the time during which the body is suspended 

 above the ground. On this method the diagram in 

 Fig. I will represent the formula of the rhythm of 



the walking pace (i), of ascending a staircase (2), of 

 running (3), and of rapid running (4). From these it may 

 be gathered that in walking the contact of one foot with 

 the ground follows that of its fellow without any interval ; 

 that in climbing a hill or going upstairs there is this 

 difference, namely, that the one foot does not leave the 

 ground until its fellow has been in contact with it a per- 

 ceptible time ; that in running there is an interval at each 

 step during which the body is quite off the ground ; and 

 fourthly, that in rapid running, though the duration of 

 each step is shortened, that of the interval is lengthened. 

 Fig. 2 represents the gallop of children, (i) being what 

 may be termed left gaUop, and (2) right gallop, according 

 to which foot is in front. This rhythm will be found in- 

 structive when we come to refer to the same in the horse. 



