DEXTKAL PREEMINENCE. 457 



on a left-handed person. The data given by Dr. Dwight 

 are not sufficient, however, to render this explanation satis- 

 factory. 1 



The most important anatomical and pathological facts 

 bearing upon the question under consideration are the fol- 

 lowing : Dr. Boyd has shown that the left side of the brain 

 almost invariably exceeds the right in weight, by about one- 

 eighth of an ounce. In aphasia, the lesion is almost always 

 on the left side of the brain. These facts point to a pre- 

 dominance of the left side of the brain, which presides over 

 the movements of the right side of the body. Again, a few 

 cases of aphasia with left hemiplegia, the lesion being on the 

 right side of the brain, have been reported as occurring in 

 left-handed persons. These points we have noted in treating 

 of the nervous system. 3 



Dr. Ogle, in a recent paper on right-handedness, gives 

 several instances of aphasia in left-handed persons, in which 

 the brain-lesion was on the right side. In two left-handed 

 individuals, the brain was examined and compared with the 

 brain of right-handed persons. It was found that the brain 

 was more complex on the left side in the right-handed, and 

 on the right side in the left-handed. 3 In the discussion which 

 followed the presentation of this paper, Dr. Charlton Bastian 

 stated that he had found the gray matter of the brain to be 

 generally heavier on the left than on the right side. 4 With 

 regard to the cause of the superior development of the left 

 side of the brain, the only explanation offered was the fact 



1 DWIGHT, Right and Left Handedness. Journal of Psychological Medicine, 

 New York, 1870, vol. iv., p. 539. 



2 See vol. iv., Nervous System, pp. 356, 357. 



3 OGLE, On Dextral Preeminence. Medico- C hirurgical Transactions, Lon- 

 don, 1871, vol. liv., p. 279, et seq. 



In this very interesting paper, Dr. Ogle discusses most of the theories of 

 dextral preeminence, and gives some very curious observations, showing that 

 this condition exists in monkeys and parrots. Most monkeys, he found, used 

 the members of the right side by preference, while a few were distinctly left- 

 handed. 



4 New York Medical Journal, 1872, vol. xv., p. 279. 



