74 HEREDITY AND EUGENICS 



of left-handedness forms such a continuous series as 

 these resuhs would indicate, although it is highly 

 probable, if not certain, that degrees of left-handed- 

 ness exist . Beeley suggests that a slightly left-handed 

 child should be taught to use its right, but that an 

 extreme left-hander should not. 



That the right hemisphere of the brain controls 

 the left side of the body and vice versa is, of course, 

 well known ; also that the development of the speech- 

 centre may be interfered with by a too early attempt 

 to teach a left-handed child to use its right hand, 

 thus leading to stuttering. 



The manner of clasping the hands, whether right- 

 handed or left-handed — i.e., with the right thumb 

 over the left or vice versa — although characteristic 

 enough for the individual, apparently bears no 

 relation to right or left-handedness. It does not 

 follow any known rule of inheritance, but appears, 

 nevertheless, to be partially inherited, for when both 

 parents show a right- or left - handed clasp the 

 majority of the children will be of the same t3^pe. 

 Statistics show that en masse the two methods usually 

 occur with equal frequenc}', but neither condition 

 breeds true. Compton (191 2) has studied the right 

 and left-handed seedlings (as regards the manner of 

 folding of the first leaf), which occur in various cereals, 

 but the condition is not inherited. Thus the seeds 

 from a left-handed (LH) plant produce the same 

 ratio of LHand RH plants as do the seeds of a right- 

 handed (RH) plant. In two-rowed barley this ratio 

 LH/RH was shown to be constant for three genera- 

 tions, and therefore inherited. In a total of 19,165 

 seedlings, the percentage of LH seedlings =58-362. 

 Seeds planted from the odd and even rows separately 

 also gave the same preponderance of left-handed 

 plants. Six-rowed barley gave a similar excess of 

 LH plants. In oats, however, there is regularly an 



