Bauhaus-Universität Weimar

Researches in cross-education. 
45- 
left hand, while much of its speed is lost while tapping with either one or 
both feet. This means simply that one arm is in closer nervous con¬ 
nection with the other arm than the upper limbs are with the lower. 
VI. Theoretical. 
An explanation of cross-education cannot as yet be completely and 
satisfactorily made. To aid in the explanation of the fact certain ex¬ 
periments of other observers are here brought together. 
Experments in diversion. 
Lombard, 1 in his work with Mosso’s ergograph, has shown that the 
strength of the right and left hands may vary either synchronously or in¬ 
dependently. By means of two ergographs he secured records of both 
hands at the same time. He concludes that the variations are not due 
to any abatement of will power or attention, or to the fatigue of muscle ; 
but rather to changes which affect the lower centers of the spinal cord. 
The variations in strength which occur synchronously are due to changes,, 
probably circulatory, affecting large parts of the central system ; those- 
which occur independently are due to local changes. 
Bryan’s* 2 experiments in tapping, carried on with children of different 
ages, prove that the effects of effort, through either extremity, are shared 
by both ; and that the tapping ability of a joint is affected by the 
simultaneous exertion of the symmetrical joint on the other side. 
Patrizi3 found that the strength of one hand variés whether it works 
alone or with the other hand. In his tests with the ergograph he found : 
(1) that in simultaneous action, the right hand could do 3.67 kgm. of' 
work, and left, 2.94, total, 6.61 ; in alternative action, right, 3.72, left, 
3.58, total, 7.30 (it should be noted that the gain in alternative action 
is made chiefly by the left hand, as if, in simultaneous action, more atten¬ 
tion were paid to the right hand than to the left); (2) that with the left 
hand in isolated action, its work was 4.63 kgm.; and with the left work¬ 
ing alternately with the right, its work was 5.64—a gain of x.oi or 
21.8%—showing that the action of the right hand reinforces that of the 
left. 
'Lombard, Some alterations in the strength which occur during fatiguing voluntary 
muscular work, Jour, of Physiol., 1893 XIV 113. 
2 Bryan, On the development of voluntary motor ability, Amer. Jour. Psych. 1892-93 
V 201. 
"Patrizi, La simultanéité et la succession des impulsions voluntaires symétriques, 
Archives Ital. de Biol., 1893 XIX 126, of which an abstract appears in the Année- 
Psych., 1894 I 452.
        

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