Page:Collected Physical Papers.djvu/288

268 to its maximum; further stimulation adds nothing to the effect, and the deflection is held, as it.were rigid,

so long as the stimulation is kept up. With lesser frequency of stimulation the tetanus is incomplete, and the curve becomes jagged (fig. 66).

Amongst living substances the nerve is practically indefatigable. Successive curves are exactly similar. Muscles, however, exhibit fatigue, which disappears after a period of rest.

Inorganic substances likewise exhibit fatigue specially after prolonged action. The fatigue curve here reproduced was obtained from tin that had been subjected to very prolonged stimulation; its remarkable similarity to the curve of fatigue in muscles will be at once