Page:Life in Motion.djvu/141

Rh more create energy than the metallic, dead steam-engine can do.

Can we show that the muscle is also the seat of chemical changes? If we can do so, we may find that there are operations going on in a muscle that are comparable to the combustions or burnings in the furnace of a steam-engine. Let us try. Here is a bit of fresh muscle. I test it with red litmus paper, a well-known test for alkalies, and you observe the paper becomes slightly blue. We find then that the reaction, as it is termed, of a quiet muscle is alkaline. The muscle is alkaline on account of certain alkaline salts of soda present in it. Let us now test a similar muscle that has been tetanised since the beginning of the lecture. You see the red litmus shows nothing. There is no blueness, as in the other case, and we conclude that the muscle is not now alkaline. But we now test it with a bit of blue litmus paper, which is the method employed by chemists to detect acids, and you see it is reddened. This reddening shows the presence of an acid substance, and careful chemical research has proved that the acidity is due to a kind of lactic acid, an acid