Page:Life in Motion.djvu/137

Rh spot of light moves to the right, proving that the thermal pile with which the muscle was in contact has become hotter, or, in other words, that the muscle in the tetanic state has become hotter.

It is not so easy to show that even a simple contraction produces heat, because such a movement of the gastrocnemius of a frog is associated only with a rise of temperature of from one-thousandth to one-