LIFE, the kind of activity characteristic of living creatures. No doubt this activity is, in its objective aspects, an integration of numerous chemical and physical processes, and there is no warrant for postulating any mysterious "vital force." On the other hand, it must be allowed that life is a unique kind of activity, for the formulae of matter and energy, electrons, protons and electro-magnetic radiations or ether-waves, as at present under stood, do not suffice to describe (a) the everyday functions of the body in their orchestration, (b) the self-preservative activities of any organism at any grade of being, (c) the purposive be haviour of higher animals well-endowed with brains, (d) the phe nomena of development and heredity or (e) the facts of evolu tion. Everyone allows that living is in part analysable into chem ical and physical processes, yet these are modified by their occur rence in the colloidal medium of the chemically very complex protoplasm. In conditions of extreme complexity, a new aspect of reality—Life--emerges. Moreover, when the chemical and physical ledger is added up, it does not give a unified description of what has actually occurred when, e.g., a migrant bird makes its journey. For to describe this it is necessary to introduce con cepts beyond physics and chemistry, such as enregistration of the past, awareness of the present and purposiveness towards the future. In at least the higher reaches of the animal kingdom, behaviour is correlated with psychical activity, incommensurable with physical processes. Thus life is an activity of organisms which requires for its description concepts transcending those of mechanism. This view does not in any way contradict the theory that living organisms may have arisen on the earth from non living materials. When the materials were complex enough and in an appropriate collocation, living organisms may have emerged.
bolic processes counterbalance the katabolic, repair counteracts waste; rejuvenescence wards off senescence. The organism is like a clock that winds itself up as it runs down. No doubt this quality is to be analysed as far as may be,—in terms, for instance, of the characteristic fermentations and their reversibility. Much depends on the fact that the proteins are always colloidal, admitting of intensity and rapidity of chemical reactions on the surface of the multitudinous ultra-microscopic particles or droplets suspended in the liquid phase. Another feature is the chemical individuality everywhere manifest, for each distinct type of organism seems to have some distinctive protein of its own, and some characteristic rate or rhythm of metabolism. Thus under the general quality of persistence amid unceasing metabolism, there is a triad of facts : (1) the building-up that compensates for the breaking-down of proteins, (2) the occurrence of these proteins in a colloidal state and (3) their specificity from type to type.
(b) A second triad of qualities includes the organism's charac teristic powers of growing, multiplying and developing. A surplus of income over expenditure is the primal condition of organic growth. As contrasted with the growth of a crystal, an organism can grow at the expense of materials more or less different from those of the growing body; it implies active assimilation, not mere passive accretion; and it is a definitely regulated process— regulated from within. Growth naturally leads to the simplest forms of multiplication or reproduction, for persistent growth tends to bring about organic instability, which may be intracellular as in unicellular organisms and in ordinary cell-division, or local ized along a line of weakness or low vitality, as in the f rag mentation of some lower multicellular animals. Asexual multi plication is a regularized form of discontinuous growth, and sexual reproduction by liberated germ-cells is a secondary specialization, anticipated in the spore-formation of many of the Protozoa and Protophyta (see REPRODUCTION).