An American text-book of physiology . support atfordeJ by the first contraction to the second, nuistalso phiy an important part, and we mnst turn to this for the completion of theexplanation of the great height acquired by the tetanus curve. Efed of Support on the Heic/ht of Contractions.—Von Kries and VonFrey - found that, in general, the shorter the distance the muscle has. to raisea .weight, the higher it can contract, and that if a muscle be excited at a regu-lar rate, and the support for the weight be raised between each of the succeed-ing contractions, at a certain height of the support
An American text-book of physiology . support atfordeJ by the first contraction to the second, nuistalso phiy an important part, and we mnst turn to this for the completion of theexplanation of the great height acquired by the tetanus curve. Efed of Support on the Heic/ht of Contractions.—Von Kries and VonFrey - found that, in general, the shorter the distance the muscle has. to raisea .weight, the higher it can contract, and that if a muscle be excited at a regu-lar rate, and the support for the weight be raised between each of the succeed-ing contractions, at a certain height of the support the contractions may beas high as during tetanus (see Fig. 52). This effect can be got with a freshmuscle when the interval between the excitations is such that there can be nosummation in Helmholtz sense. The importance of this discovery to our understanding of tetanus is verygreat, for it has been found that if an unsupported muscle be rapidly excited,effects are observed which closely resemble those obtained by the aid of a sup-. FiG. 53.—Effect of a gradually Increasing rate of excitation. Excitation of a gastrocnemius muscleof a frog with breaking induction shocks of medium strength. Tlic time was recorded directly, by atuning-fork making 100 vibrations per second. The rate of excitation was gradually increased, andthen gradually decreased. The ascending curve, a-b, shows the effect of increasing, and the descendingcurve, c-d, of decreasing the rate of stimulation. Excitation was given by means of a special mechanism•for interrupting the primary circuit of an induction apparatus and at the same time short-circuiting themaking shocks. This interrupter was run by an electric motor which was allowed to speed up slowly,and was slowed down gradually. port; this we have seen in the experiments recorded in Figures 47, 48, p. llf).After a certain amount of excitation, a change occurs in the condition of amuscle, owing to which it acts as if it had received an upward push, an
Size: 1933px × 1292px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookautho, bookcentury1800, bookdecade1890, booksubjectphysiology
