Page:Philosophical Review Volume 2.djvu/85

Rh gave parallel results, save that in the fatigued state the "lateral effects" are much less diminished in proportion than are the longitudinal ones, and that the spring is thus a much more sensitive indicator of fatigue than the bag. The maximal faradic shortening is much less than the maximal voluntary shortening, yet the "hardening" or lateral effects may be as great in the one case as in the other. The lateral effect slightly outlasts the shortening; and outlasts it considerably in fatigue, more especially in voluntary fatigue. It may in the latter case momentarily increase whilst the muscle is actually lengthening. These facts, according to W., point to the two distinct processes, lateral and longitudinal, in muscular contraction, which fatigue may dissociate. The protraction of the lateral process in voluntary fatigue he considers to show a continued influence from the fatigued centre, a "residual discharge" able only to harden but not to shorten the muscle. A cut-out frog's muscle also shows the lack of congruence of the lateral and longitudinal effects, for the shortenings successively diminish during faradic fatigue whilst the lateral effects show no such decline. Prof. Müller, on his part, entirely objects to W.'s interpretation of the results of his bag-method. It is contrary to generally received doctrines, he says, to suppose swelling without shortening in muscle, or hardening after inner tension has ceased. The records of Waller's "bag," he thinks, are due to contraction of antagonists, and to afflux of blood into the muscles, especially when the latter are faradically exercised. As for the frog's muscle, he points to the possibility of a mechanical elongation of the muscle's own length by its treatment as a sufficient explanation of Waller's results. This (which has been observed) would naturally give diminished tracings of shortening with undiminished tracings of swelling.

Dr. Waller finds still other peculiarities in fatigue. Using Method 3, that of the "ponograph," he finds the upward spring of an arm suddenly released from the weight it has been upholding to be greater in fatigue than when the arm is fresh. He considers that this fact is probably connected with the protraction (just described) of the "lateral effect" in fatigue, and that it looks, therefore, more like a residual central effect than like a peripheral effect. The centres, therefore, here again would seem to take the lead in voluntary fatigue. He finds, moreover, that when the two hands, one being fatigued, the other fresh, work simultaneously, each upon a dynamograph, the relaxations of the fatigued hand take place less promptly than in the other. W. candidly admits that all these phenomena may be, whilst M. insists that they probably are, purely peripheral in their origin.

W. then repeats and discusses experiments by Fick and Mosso which show that a maximal voluntary contraction, so far from being increased, is diminished when a faradic stimulation is added. The "step-down"