Volltext: Researches in cross-education (second series) (8)

Walter W. Davis. 
the will had been exerted to its utmost for ten successive pressures. The 
gain made by this group must be attributed to the development of voll 
tional power. This gain was shared in by the left hand, unpracticed 
the amount in its favor being due to the effects of fatigue on the right 
hand after three weeks of practice. 
It is apparent that both factors were present in Group B. The gain 
of the left hand, unpracticed, was 13.2 lbs., 69% greater than its gain 
in Group A. Theoretically this 69% may represent the influence of 
coordination in causing a gain of strength, compared with 100% as 
representing the gain due to the development of volition. 
The subjects of Group IV. made practically no development with 
either hand. There was a slight gain with the right and a loss with the 
left. This was true of the women too, though the left did gain slightly 
at the second final test. The method of practice seems altogether 
unfavorable to the development, in any effective sense, of either volition 
or coordination. It is probable that volition is developed in a limited 
degree but that the gain due to this development is counteracted by 
what may be termed a loss of coordination. The subject having 
become accustomed to the shape of one instrument has learned to 
use certain muscles after a certain order or fashion. At the final test, 
using a differently shaped instrument but with the same object in view, 
the tendency may be to use the same muscles in the same series or 
order as in the practice with the stick. The result is a lack of such 
coordination as will be effective for a good test with the dynamometer. 
One set of muscles obeying a mistaken impulse behind it, gets in the way 
of the set that should respond. The loss of effectiveness in one factor 
counteracts the gain in the other. 
For the same reasons there would not be a great development of vo¬ 
lition in Group II. Coordination was probably responsible for the 
greater part of the gain. The gain is not so large as that of Group B, 
where both factors work at their best and in harmony with each other. 
The results and observations seem to point to the conclusion that prac¬ 
tice with the dynamometer develops two factors chiefly—volition and 
coordination. The development of these factors cause a gain in strength 
of each hand whether practiced or unpracticed. Both factors are among 
the faculties that we call mental. 
It is not asserted that other factors may not run parallel with these. 
In fact it seems probable that the storing up of energy in the motor cells 
of the brain is a necessary concomitant with the development of volitional 
power. This is indicated by the results that were apparent all through 
the experiments, which are plainly due to fatigue. The most probable


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