| B. Physiology = The Science of Functions. Physics and chemistry of the organism. | |
| B I. Ergology. 5. Vegetal ergology. Physiology of the vegetative functions. 5a. Trophonomy. The science of metabolism.5b. Gonimatology. The science of reproduction. —— 6. Animal ergology. The science of movement. 6a. Phoronomy. The science of movement. 6b. Sensonomy. The science of sensation 6c. Psychology. | B II. Perilogy. Physiology of relations. 7. Chorology. The science of distribution. —— 8. Œcology. (or bionomy or ethology). The science of domestic life. Biological economy. Relations of the organism tothe environment, and to otherorganisms with which it lives. |
V
DEATH
Life and death—Individual death—Immortality of the unicellulars—Death of the protists and tissue-organisms—Causes of physiological death—Using up of the plasma—Regeneration—Biotonus—Perigenesis of the plastidules: memory of the biogens—Regeneration of protists and tissue-organisms—Senile debility—Disease—Necrobiosis—The lot of death—Providence—Chance and fate—Eternal life—Optimism and pessimism—Suicide and self-redemption—Redemption from evil—Medicine and philosophy—Maintenance of life—Spartan selection.
Nothing is constant but change! All existence is a perpetual flux of "being and becoming"! That is the broad lesson of the evolution of the world, taken as a whole or in its various parts. Substance alone is eternal and unchangeable, whether we call this all-embracing world-being Nature, or Cosmos, or God, or World-spirit. The law of substance teaches us that it reveals itself to us in an infinite variety of forms, but that its essential attributes, matter and energy, are constant. All individual forms of substance are doomed to destruction. That will be the fate of the sun and its encircling planets, and of the organisms that now people the earth—the fate of the bacterium and of man. Just as the existence of every organic individual had a beginning, it will also undeniably have an end. Life and death are irrevocably united. However, philosophers and biologists hold very different views as to the real causes of this destiny. Most of their opinions are at once out of court, because they have not a clear idea of the nature of life, and so can have no adequate idea of its termination—death.
The inquiry into the nature of organic life which we instituted in the second chapter has shown us that it is, in the ultimate analysis, a chemical process. The "miracle of life" is in essence nothing but the metabolism of the living matter, or of the plasm. Recent physiologists, especially Max Verworn and Max Kassowitz, have pointed out, in opposition to modern vitalism, that "life consists in a continuous alternation between the upbuild and the decay of the highly complicated chemical unities of the protoplasm. And if this conception is admitted, we may rightly say that we know what we mean by death. If death is the cessation of life, we must mean by that the cessation of the alternation between the upbuild and the dissolution of the molecules of protoplasm; and as each of the molecules of protoplasm must break up again shortly after its formation, we have in death to deal only with the definite cessation of reconstruction in the destroyed plasma-molecules. Hence a living thing is not finally dead—that is to say, absolutely incompetent to discharge any further vital function—until the whole of its plasma-molecules are destroyed." In the exhaustive justification with which Kassowitz follows up this definition in the fifteenth chapter of his General Biology, the natural causes of physiological death are fully described.
Among the numerous and contradictory views of recent biologists on the nature of death we find many errors and misunderstandings, due to a lack of clear distinction between the duration of the living matter in general and that of the individual life-form. This is particularly noticeable in the contradictory views which have been elicited by August Weismann's theory (1882) of the immortality of the unicellulars. I have shown in the eleventh chapter of the Riddle that it is untenable. But as the distinguished zoologist has again taken up his theory with energy in his instructive Lectures on the Theory of the Descent (1902), and has added to it erroneous observations on the nature of death, I am obliged to return to the point. Precisely because this interesting work gives most valuable support to the theory of evolution, and maintains Darwin's theory of selection and its consequences with great effect, I feel it is necessary to point out considerable weaknesses and dangerous errors in it. The chief of these is the important theory of the germ-plasm and the consequent opposition to the inheritance of acquired characteristics. Weismann deduces from this a radical distinction between the unicellular and the multicellular organisms. The latter alone are mortal, the former immortal; "between the unicellular and the multicellular lies the introduction of physiological—that is to say, normal—death." We must say, in opposition to this, that the physiological individuals (bionta) among the protista are just as limited in their duration as among the histona. But if the chief stress in the question is laid, not on the individuality of the living matter, but on the continuity of the metabolic life-movement through a series of generations, it is just as correct to affirm a partial immortality of the plasm for the multicellulars as for the unicellulars.
The immortality of the unicellulars, on which Weismann has laid so much stress, can only be sustained for a small part of the protists even in his own sense—namely, for those which simply propagate by cleavage, the chromacea and bacteria among the monera (chapter ix.), the diatomes and paulotomes among the protophyta, and a part of the infusoria and rhizopods among the protozoa. Strictly speaking, the individual life is destroyed when a cell splits into two daughter-cells. One might reply with Weismann that in this case the dividing unicellular organism lives on as a whole in its offspring, and that we have no corpse, no dead remains of the living matter, left behind. But that is not true of the majority of the protozoa. In the highly developed ciliata the chief nucleus is lost, and there must be from time to time a conjugation of two cells and a mutual fertilization of their secondary nuclei, before there can be any further multiplication by simple cleavage. However, in most of the sporozoa and rhizopoda, which generally propagate by spore formation, only one portion of the unicellular organism is used for this; the other portion dies, and forms a "corpse." In the large rhizopods (thalamophora and radiolaria) the spore-forming inner part, which lives on in the offspring, is smaller than the decaying outer portion, which becomes the corpse.