476 LEFTHANDEDNESS. 



middle lobes of the brain on the left side were in a more advanced 

 condition than those on the right side, the balance being maintained 

 by an opposite condition of the posterior lobes. Hence, in consequence 

 of the well-known decussation of the nerve-roots, the right side of 

 the body— so far as it is influenced by brain-force — would, in early 

 foetal life, be better supplied with nervous force than the left side ; 

 and thereby movements of the right arm would precede and be more 

 perfect than those of the left. 



This statement of Gratiolet, relative to the earlier development of 

 the left than of the right side of the brain, has been challenged by 

 other observers ; but many phenomena accompanying certain local 

 injuries of the brain lend confirmation to the theory that the left 

 lobe of the brain influences the action of the organs on the right 

 side of the body, and vice versa. 



" The opinion," says Dr. ?ye-Smith, " that some difllerence between 

 the two sides of the brain has to do with our preference for the right 

 hand over the left may, perhaps, be supported by two very interesting 

 cases of aphasia occurring in lefthanded persons, recorded by Dr. 

 Hughlings Jackson and Dr. John Ogle. In both these patients there 

 was paralysis of the left side, so that it seems likely that in these two 

 lefthanded people the right half of the brain had the functions, if 

 not the structure, which ordinarily belong to the left. To these cases 

 may be added a very remarkable one published by Dr. Wadham 

 (St. George's Hosp. Rep. 1869). An ambidextrous, or partially left- 

 handed lad was attacked with left hemiplegia and loss of speech ; he 

 had partly recovered at the time of his death, twelve months later, 

 and then the right insula, and adjacent parts, were found softened." 



The remarkable difference in the convolutions of different brains, 

 and the consequent extent of superficies of some brains over others 

 apparently of the same size, have been a matter of special observation ^ 

 with results lending confirmation to the idea that great development 

 of the convolutions of the brain is the concomitant of a correspond- 

 ing manifestation of intellectual activity. But the degree of develop- 

 ment, and the com.plexity in the arrangement of these convolutions, 

 often differ considerably in the two hemispheres of the same brain ; 

 and it seems not improbable that lefthandedness may prove to be 

 traceable to certain structural differences between the right and left 

 hemispheres. The vai-iations in shape and arrangement of the con- 

 volutions in either hemisphere may be no more than the accidental 



