72 PHYSICAL EXPRESSION. 



of movements in man or in animals, but we 

 have to establish rules by which we may dis- 

 tinguish the co-ordinated from the iDCO-ordinated 

 movements. When a man walks steadily along 

 a road we see that his movements are regular, 

 there is a similar repetition of events, and similar 

 impressions are left at equal intervals upon the dust 

 of the road ; such a man's movements in walking- 

 are said to be co-ordinate, and the regularity in the 

 successions and combinations of his movements, as 

 indicated by the general regularity of the move- 

 ments of his whole body and the uniformity of his 

 foot-prints, indicates to us the perfect co-ordination 

 of his movements in walking. 



Contrast the movements of such a good walker 

 with those of a man afflicted with the condition 

 termed locomotor ataxy, and contrast the foot- 

 prints left by the two men. In locomotor ataxy 

 the patient walks with a precipitate gait, and 

 staggers, the legs start hither and thither vaguely, 

 and the heels come down at each step as in 

 stamping. Such movements are said to be inco- 

 ordinate. Our present object is to inquire how 

 we can best define and formulate what we mean 

 by co-ordination. This, I believe, can only be done 

 with scientific exactness by definitions framed 

 in terms of combinations and successions of move- 

 ments and results of movements. 



Locomotion, or walking, has been described and 

 experimented upon in man by M. Marey.* He 

 says, " The most simple and usual pace is walking, 



* tl Animal Mechanism," p. 111. 



