DARWIN MEMORIAL. 91 



were obscure before this discovery, can now be satisfactorily ex- 

 plained. Among these are the phenomena of associated move- 

 ments. It has been stated that the variety and complexity of the 

 movements involved in the simple act of walking are such that it 

 would be impossible ever to perform it were it necessary to think 

 what had to be done, and weigh in the judgment the precise amount 

 of force necessary to distribute to each muscle at each moment of 

 the act. It is now known that the cerebral centers which control 

 the separate muscles put in action are closely contiguous in the 

 brain, and that they probably intercommunicate and excite each 

 other in a definite manner, predetermined by habit and heredity. 

 The conscious mind has only to set in motion the subordinate ap- 

 paratus, when it goes on, and works out the problem with matchless 

 skill, like the system of cogs and eccentrics that produce the intri- 

 cate pattern in an engraver's lathe. All have noticed the uncouth 

 manner in which children and untrained persons follow with lips 

 and tongue the motions of their hands when using a tool of any 

 kind. Darwin ascribes this to unconscious imitation, but it can be 

 explained more strictly in accordance with his own principles. 

 The facial muscles are actuated from a cerebral center in close 

 proximity to those which move the arms and hands. In the lower 

 animals this is necessary, for the mouth is an organ of prehension, 

 used in strict association with the fore-limbs in seizing prey, and in 

 other acts. As this associated movement became strongly fixed by 

 long habit, it survives with great obstinancy, and though it has not 

 been useful to the race since the historical period, we have yet to 

 caution our children not to put their tongues out when they write. 



My limit of time forces me to conclude this hasty and imperfect 

 summary. The practical bearing of these views is not without im- 

 portance. Physicians have always depended greatly upon emo- 

 tional expression as a means of diagnosis. Unconsciously the face 

 of the patient reveals his physical state. Yet too much has been left 

 in the empirical border-land of science. Why a certain pathologi- 



