THE ORIGIN OF RIGHT-HANDEDNESS. 611 



halves of the body. As she had not learned to speak or to utter 

 articulate sounds with much distinctness, we may say also that 

 right or left handedness may develop while the motor speech 

 center is not yet functioning. 



5. In most cases involving the marked use of one hand in prefer- 

 ence to the other, the second or backward hand followed slowly 

 upon the lead of the first, in a way clearly showing symmetrical 

 innovation of accompanying movements by the second hand. This 

 confirms the inference as to such movements drawn from the 

 phenomena of mirror-writing, etc., by Fechner and E. H. Weber. 



Some interesting points arise in connection with the interpre- 

 tation of these facts. If it be true that the order of rise of mental 

 and physiological functions is constant, then for this question the 

 results obtained in the case of one child, if accurate, would hold 

 for others apart from any absolute time determination. We 

 would expect, therefore, that these results would be confirmed by 

 experiments on other children, and this is the only way their cor- 

 rectness can be tested.* 



If, when tested, they should be found correct, they would be 

 sufficient answer to several of the theories of right-handedness here- 

 tofore urged. The phenomenon can not be due to differences in 

 balance of the two sides of the body, for it arises before the body 

 begins to stand erect. It can not be due to experience in the use 

 of either hand, since it arises when there is no such difference of 

 experience, and since the hand j^referred is used, as a matter of 

 fact, for purposes for which in experience the other would be alto- 

 gether more convenient.! The rise of the phenomenon must be 

 sought, therefore, in more deep-going facts of physiology than 

 such theories supply. 



If, on the other hand, heredity be brought to the aid of these 

 " experience " theories, it is possible to claim that, as structure is 

 due to function, experience of function must have been first ; and 

 only thus could the modification in structure which is now suffi- 

 cient to produce right-handedness in individual cases have been 

 brought about. On the other hand, if we go lower in the animal 

 scale than man, analogies for the kinds of experience which are 



* Vierordt says concerning such experiments : " Adequate observations are wanting on 

 the grasping movements of the infant's left and right arm a liind of observations which 

 would be of the first importance for this inquiry " (Physiologic des Kindesalters, p. 428) ; 

 and Wilson : " Only a prolonged series of observations, such as those by Prof. Baldwin 

 already noted, made at the first stage of life, and based on the voluntary and the un- 

 prompted actions of the child, can supply the needful data " (Left-handedness, p. 209). 



f An additional point, which I think is true, is that a right-handed child learns to shake 

 hands properly using the more inconvenient hand across his body more easily than the 

 left-handed child. 



