Life cannot be defined as the sum of the attributes of living things. Nevertheless we may conceive that one attribute may be sufficiently constant to serve as the diagnostic sign of life. This is what Mr. Tashiro has demonstrated. "That mechanism," he says, "which enables living matter to respond to the external world . . . may be called the most characteristic thing in life. The chemical accompaniment, or basis, of this mechanism, discovered by the author in nerve fibers, he has hoped to show exists in all forms of living matter, both of plants and animals. It gives a chemical method of distinguishing living from dead tissue, and of measuring the quantity of life."

"A hundred years ago," Mr. Tashiro reminds us, "the electrical sign of life was discovered by Galvani, when he found that animal tissues are a source of electricity. ... It is now certain that whenever the response to a stimulus takes place in animals or plants-the response which is the sign of life-an electrical change accompanies it. . . . There is always and everywhere," he continues, "an accompanying chemical change of a particular kind which is as sure a sign of life and as invariable an accompaniment of the vital reaction as the electrical change. This chemical sign is the sudden outburst of carbon dioxide which all living things show-plants as well as animals, dry seeds as well as the nerve tissues of the highest mammals-when they are stimulated in any way."