10 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



present any peculiarity of arrangement in left-handed 

 people. 



The theory of M. Acquille Combe* suggests that the 

 foetus in uiero rests with its left side pressing against the 

 maternal spina] column, that the pressure interferes with 

 muscle development on the left side. If the foetus chances 

 to rest in the opposite position the right side is pressed 

 upon and the individual becomes eventually left-handed. 

 An ingenious hypothesis, but it does not cover the cases 

 of the parrots nor of the invertebrates. 



Professor G. Y. Pooret attributes right-handedness 

 to the extra weight of the viscera on the left side of the 

 thorax in man and some other vertebrates. Professor 

 Strutliers,+ on the other hand, points out that the viscera 

 of thorax and abdomen combined are in man from fifteen 

 to twenty ounces heavier on the right side than the left. 

 He considers this extra weight on the right side has 

 produced a greater development of the right leg, and as 

 a consequence (though I fail to see why) of the right arm 

 also. 



A fourth theory regards right-handedness simply as the 



result of habit founded on accidental variation, which 



has become a permanent condition through affording 



certain advantages in the way of protection, etc. In other 



words we bring it under the same law as the asymmetry 



of the invertebrates. Dr. Pye SniithlF has an ingenious 



hypothesis (improving upon that of Bichatll) regarding 



the detailed mode of the production of this habit in man. 



lie thinks that as man is and always has been a combative 



animal, whose method of fighting, until quite recent times, 



•Journal de Physiologic. f Lancet, 10th April, 1807. 



; Ed. Med. Journal, 1803, and Lancet, 17th April, 1897. 



«' Guy's Hosp. Reports, 1871, p. 111. 



|| ' La Vie et la Mort.' 



