LEFTHANDEDNESS. 475 



observation in Guy's Hospital, where the subjects of the abnormal 

 disposition of the viscera had been righthanded. 



Dr. Struthers has shown from a series of very carefully conducted 

 observations by himself and others, that " as far as the viscera alone 

 are concerned, the right side is at least 22| ounces heavier than the 

 left, and that this is reduced 7f ounces by the influence of the con- 

 tents of the stomach, leaving a clear preponderance of at least 1 5 

 ounces in favour of the right side." The preponderance of the right 

 side, he adds, is probably considerably greater than 15 ounces, and 

 it is rendered still more so in the erect postiu-e. The total weight of 

 viscera on the right side he states at 5 Of ounces, while that of the 

 left side is only 28 ounces, giving a visceral preponderance on the 

 right side of 22| ounces, which he reduces, as above stated, by 

 deducting Tf ounces for the contents of the stomach. But if this 

 relative excess of weight on the right side be the true eause of the 

 prevalent righthandedness, the transposition of the viscera ought to 

 be invariably accompanied with a corresponding lefthandedness ; 

 whereas this is proved not to be the case. 



The other theory, which refers lefthandedness to the abnormal 

 arrangement of the blood-vessels, and especially of the right and left 

 subclavian artery, is more difficult to test, since, with rare exceptions, 

 the evidence lies beyond reach of observation in the living subject. 

 So far, however, as ascertained facts can be appealed to, they fail to 

 sustain the theory. Dr. Pye-Smith states that he found the deviation 

 from the normal arrangement of the primary branches of the aorta, 

 in which the right subclavian arises from the third part of the aortic 

 arch, occur four times in 296 dissections. As this variation, he says, 

 " cannot be recognized during life, its connection with lefthandedness 

 is not easy to investigate. But in one case, at least. Dr. Peacock 

 ascertained for me that the subject of this abnormality, whose heart 

 and arteries he had examined for another purpose, was righthanded 

 during life." 



It thus appears that the source of right or lefthandedness is not 

 traceable either to the transposition of the viscera, or to the dis- 

 position of the subclavian arteries. We are therefore led to seek for 

 a physical cause for the preferential use of the one or other hand in 

 the central nervous system. In this direction the eminent anatomist. 

 Professor Glratiolet, looked for a solution of the difficulty. He main- 

 tained that in the early stages of foetal development, the anterior and 



