BIOLOGY. but we have not yet noted the most essential characteristics of "the dog's actions. They are significant. They have a meaning. They stand in judicious adjustment to the canine world. Whether he shuts his eyes, throws back liis cars, and, straightening his tail, plants his teeth in my leg, or crouches at my feet with his muscles re- laxed, his ears pendant, and his tail trailing, or, putting his tail between his legs, runs away howl- ing, the reason for his conduct is not the me- chanical impact of the blow, nor the pain which it causes, but the unportance of escape from the further injury which may follow. The means he adopts arc those which have been favorable to this result in the past history of dogs. It is clear that the meaning of the dog's actions can never be learned by studying his body; for if the meaning which we apprehend is embodied in any structure it must be in our own rather than that of the dog. The dog no doubt knows, just as we do, that in the natural course of events the attack is a sign of a disposition to do him further harm, and that he may arrest or avert this by doing something on his own part to meet it and prepare for it: but we know, in the case of most organisms, only the response and not the con- sciousness of it. The imi)ortant point, however, is this: The kick is a sign of something that may follow, and the responsive actions are not the mechanical equivalent of the kick; for they are directed or adjusted, either with or without consciousness and reason, to an event of which it is only the forerunner or sign. The changes in the stone are the efl'ect of the blow, while the changes in the dog are, in some way, the result of the past history of the dog and of his ancestors; for, all through this history, violent assaults have been associated with danger of further vio- lence. This difl'erenee is as wide as the difference between life and its absence; and the independ- ence of biology as a science is due to its existence. It is what Herbert Spencer means by the dictum that life consists in the continm)Us adjustment between internal relations and external relations; and it is what .ristotle means by teaching that the essence of a living being is not what it is made of nor what it d(K's, but why it does it. A living being is a being that responds to the changes which go on in the world around it, for life consists in the maintenance of adjustment be- tween the changes that go on in the external order of nature and those that take place in the living body. Life is response to the established order of external nature; for the responsive actions of living beings are such that our own reason approves them as judicious and rcas(mable and likely to prove beneficial. This truth has often found expression in the statement that living things use the properties of the world around them for their own good, or that of their species. The same thought may be expressed by the statement that life is the use of the natural language of signs, for each stimulus to a vital act is, in course of nature, a sign with a signif- icance ; and the act is itself a response to the significance of which, in course of nature, the stimulus is the sign. Physical analysis resolves living beings into organs and tissues and cells and physiological units and organic compounds and molecules and atoms; and it may some day enable us to con- struct a living organism by the combination of the proper elements. Physiology resolves vital 88 BIOLOGY. activity into 'functions,' and it may some day express these functions in terms of motion ; as may also the psychology which investigates the elementary constituents of mental "faculty.' A living being is, no doubt, an organic compound, but, to the biologist, it is also something more. It is a coiirdinated whole ; a member of a species ; a part of the sum of life ; and a constituent of the universe, which would cease to lie what it is if nature were different. The biologist finds in it no self-sustaining power and no reality that would endure if it were abstracted from the natu- ral world of which it is a part. Surely, this is good sense and good science. No physiologist who studies the waste and repair of living bodies, no naturalist who knows living beings in their homes, no embryologist who studies the intluence of external conditions upon development, can for an instant admit that living beings are self- sutlicient or self-sustaining, or that their being is in themselves. For the line we draw, for lietter study, between living beings and the external world, is not one that we find in nature, but one that we make for ourselves by abstraction and generalization. The external world of a living thing is as much a part of it as its histological structure. If the environment of its body or of any cell or molecule within its body were diflcrent, neither cell nor body would be what it is; and if they had no environment they would not be at all, for neither cells nor eggs nor seeds nor desiccated rotifers exist abstractedly, A sclf-sunicieiit and self-contained living being is as fabulois as a griffm or a centaur, but no naturalist thinks fnr an instant that this tritli casts any doubt upon the real existence of living beings. It is not the real existence, but the abstract existence of living things, that the cautious biologist must dispute. Jlay not the truth that biology is the physics and chemistry of living beings be true only when it is joined with the converse truth that physics and chemistry are part of biology? It is only as living beings that we care to know. If the modest biologist were to assert that the biologi- cal aspects of the physical sciences are the only basis for rational interest in these sciences, liis good friends in physical and chemical labora- tories would no doubt charge him with arro- gance, although the.v must admit that the prin- ciples of science, as distinguished from the con- crete sciences, are i)art of biology. We cannot investigate response to the order of nature without asking what the order of nature is. What are the properties of things and of thought that c<mvince us of its existence? What is this C(mviction worth? What are the methods by which knowledge of this order is acquired and perfected and extended? How far are these methods and instruments trustworthy? .Are any limits to their application known, and. if so. how known? To all these questions the biologist has n peculiar right to ask answers, in addition to the right which he shares with other stiulents of science. The inquiry into the origin of those use- ful properties in the employment of which lifr consists is the most fascinating .and instructive intellectual occupation within the whole range of human inquiry, for to it knowledge itself owes its significance. SlONIFICANCE OF 'FiTNESS' THE FotlNDATION OP HlOl.OdV. The distinctive problem of biology, the
