[38] For a fuller development of this subject the reader is referred to an article by the author, entitled “Critical Periods in the History of, and their Relation to, Evolution” (“American Journal of Science,” vol. xiv, p. 99, 1877).
[39] “Reflex Action and Theism,” William James, “Unitarian Review” for November, 1881.
[40] See an article by the author on this subject, “American Journal of Science,” series ii, vol. xxviii, p. 305, 1859, and in “Popular Science Monthly,” vol. iv, p. 156, 1873.
[41] All chemical compounds are dissociated by sufficient heat.
[42] The origin of vital from chemical force in the green leaves of plants can not be doubted; but this does not, of course, explain the mystery of the first origin of life on the earth, for one condition of the change now is the contact of living matter.
[43] I know it is the fashion to ridicule the use of the terms vitality, vital force, as a remnant of an old superstition; and yet the same men who do so use the terms gravity, electricity, chemical force, etc. Vital force is indeed correlated with other forces of Nature, but is none the less a distinct form of force, far more distinct than any other unless it be the still higher form of psychical, and therefore it better deserves a distinct name than any lower form. Each form of force gives rise to a peculiar group of phenomena, and the study of these to a special department of science. Now, the group of phenomena called vital is more peculiar, more different from other groups than these are from each other, and the science of physiology is a more distinct department than either physics or chemistry, and therefore the form of force, which determines these phenomena, is more distinct and better entitled to a name than any physical or chemical force.
[44] “Princeton Review” for May, 1884.
[45] “Popular Science Monthly,” December, 1873.
[46] For a fuller statement of this antithesis, see an article by the author entitled “Evolution in Relation to Materialism,” “Princeton Review,” for March, 1881.
[47] Johnstone Stoney, “Nature,” vol. xxxi, p. 422.