592 



SCIENCE. 



[N.S. Vol. XIX. No. 4S4. 



see no reason so far for this left-side placing 

 of the speech-center. 



Precision in running, fighting, defense, 

 manipulation, distant vision of enemies, signs, 

 etc., would begin at least early in the history 

 of human savages, and winning in the strug- 

 gle for existence even so early would depend 

 generally far more on accuracy and perfection 

 of vision than of manual dexterity. I have 

 not been able to conclude as to the existence 

 of any degi-ee of right-handedness or left- 

 handedness or of right-eyedness or left- 

 eyedness, in animals. Beavers and monkeys 

 might possibly show the beginnings of dif- 

 ferentiation. In all human beings, of any 

 degree at least of civilization, both facts 

 can be demonstrated. When civilization is 

 present, the demonstration is apparent in the 

 right-handedness of archers, and those using 

 weapons of battle, and especially of gunners. 

 All military regulations require the musket to 

 be brought to the right shoulder in aiming 

 and firing. These and many other right- 

 handed uses and customs, of course, presup- 

 pose and make necessary right-eyedness. In 

 mechanical occupations all tools are made for 

 the right-handed. Locomotive engineers sit 

 on the right-hand side of the engine; that 

 this is because of right-eyedness is proved by 

 the fact that the throttle is manipulated by 

 the left hand, the other and the more expert 

 and stronger one being unused during the 

 ' run.' But, if right-eyed, the engineer can 

 see the track and signals better from the right 

 side of the boiler than from the left. The 

 great mystery and the long-discussed problem 

 of the varying xisage of the drivers of wagons, 

 carriages, etc., in passing on the right or left, 

 will be explained, I suspect, by right-eyedness. 

 That those afoot always pass to the right, 

 €ven though the carriages in the same street 

 pass to the left, is explained by the fact that 

 the field of vision in front and the choice of 

 directions are better under the circumstances 

 than it would be with the right-eyed passing 

 to the left. The danger of collision of 

 vehicles makes passing to the left the pref- 

 erable and safer plan. 



When the harp grew into the dulcimer, and 

 that into the piano, the execution of the most 



important, skilled and difficult part, the 

 melody or air, was of course given to the right- 

 hand side of the key-board, and the easier and 

 accompanying part to the left. But prior 

 to that was the violin, and it is only the 

 theory of right-eyedness that can explain 

 why the most diflficult and rapid fingering 

 was given to the more inexpert left hand, 

 and the simpler and easier bowing to 

 the more dextrous right. The advantage 

 was unconsciously recognized and uncon- 

 sciously applied which comes from the learn- 

 er's greater ability to see the motions and 

 positions of the fingers with the right eye 

 when the fingering is done with the left hand. 

 The left hand and the neck of the instrument 

 in this position are seen at an angle, and, 

 therefore, more correctly, than wovild be pos- 

 sible if the right hand were used for fingering 

 and the neck of the violin placed directly in 

 the line of the axis of vision of the right eye. 

 In this case there would be the difiiculty and 

 doubt which results from the foreshortening 

 or from looking along a line or surface nearly 

 level with the eye. 



The more expert hand in shooting a gun is 

 used for the simple task of pulling the trigger, 

 while the weaker and more awkward left is 

 forced to do the all important tasks of sup- 

 porting the gun and taking aim or directing 

 the barrel upon the mark. The right eye 

 compels also this reversal of what would 

 otherwise be the natural and unconsciously 

 preferred custom. In chopping, hoeing, 

 shoveling, etc., the weaker left gives the force 

 and direction of the blow, and the right only 

 guides a little the end of the tool, and in gen- 

 eral serves a subordinate function. In these 

 occupations the angled axis of vision as in 

 the violin is not necessary, and would even 

 be a disadvantage. Looking downward, as in 

 writing, the right does its work more accu- 

 rately when straight below. 



Any number of similar examples will come 

 to mind of the influence of right-eyedness in 

 every department or phase of our life, and 

 the explanation of a multitude of incon- 

 gruities and peculiarities observed or hitherto 

 unsuspected will be brought to light. There 

 is hardly any act or custom, personal or social, 



