PHYSIOLOGY 21 different parts of the body to different katastates with different composition and different properties, the various activities of the body being the outcome of the various properties of the various katastates. If this be admitted, it almost inevitably follows that what we have called proto plasm cannot be always the same thing, that there must be many varieties of protoplasm with different qualities and with correspondingly different molecular structure and composition. If this be so, the question naturally arises, why use the word protoplasm at all, since, by the showing, it seems to have no exact meaning 1 But it has an exact meaning. All the evidence at our disposal goes to show that a katastate of any given degree cannot form a fresh katastate of the same degree ; any one katastate can only arise from the decomposition of a preceding more complex katastate, and that in turn from a katastate still more complex. Passing upwards, we come at last to something which, instead of proceeding from a more complex sub stance, builds itself up out of a less complex, more simple substance, and it is this something, whatever its exact composition, into whatever katastates it is destined to fall asunder, to which the generic name " protoplasm " should be given. Possibly another new name were better, but there are advantages in retaining the old term. It is protoplasm in this sense which is alone living ; it is its synthetic power which is its token of being alive. That synthetic power is, we must admit, exercised along the ascending series of anastates. But here our knowledge is a blank ; and it would be simply waste of time to speculate as to the details of the constructive processes. Using the word "protoplasm" in this sense, it is obvious that the varieties of protoplasm are numerous, indeed almost in numerable. The muscular protoplasm which brings forth a contractile katastate must differ in nature, in com position that is, in construction from glandular proto plasm, whose katastate is a mother of ferment. Further, the protoplasm of the swiftly contracting striped muscular fibre must differ from that of the torpid smooth unstriated fibre ; the protoplasm of human muscle must differ from that of a sheep or a frog ; the protoplasm of one muscle must differ from that of another muscle in the same kind of animal ; and the protoplasm of Smith s biceps must differ from that of Jones s. We may, for a moment, turn aside to point out that this innate difference of protoplasm serves to explain the con clusions to which modern investigations into the physiology of nutrition seem to be leading. So long as we speak of muscle or flesh as one thing, the step from the flesh of mutton which we eat to the flesh of our body which the mutton, when eaten, becomes, or may become, does not seem very far ; and the older physiologists very naturally assumed that the flesh of the meal was directly, without great effort and without great change, as far as mere chemical composition is concerned, transformed into the muscle of the eater. The researches, however, of modern times go to show that the substances taken as food undergo many changes and suffer profound disruption before they actually become part and parcel of the living body, and conversely that the constructive powers of the animal body were grossly under-rated by earlier investigators. If one were to put forward the thesis that the proteid of a meal becomes reduced almost to its elements before it undergoes synthesis into the superficially similar proteid of muscle, the energy set free in the destruction being utilized in the subsequent work of construction, he might appeal with confidence to modern results as supporting him rather than opposing him in his views. It would almost seem as if the qualities of each particle of living protoplasm were of such an individual character that it had to be built up afresh from almost the very beginning ; hence the im mense construction which inquiry shows more and more clearly every day to be continually going on as well in the animal as in the vegetable body. Taking into consideration all the fine touches which make up the characters of an individual organism, and remembering that these are the outcome of the different properties or activities of the several constituent tissues of the body, working through-a delicately-balanced complicated machinery, bearing in mind the far-reaching phenomena of heredity by which the gross traits and often the minute tricks of the parents body are reproduced in the offspring, if there be any truth at all in the views which we have urged, tracing the activities of the organism to the con stitution of its protoplasm, this must be manifold indeed. The problems of physiology in the future are largely con cerned in arriving, by experiment and inference, by the mind s eye, and not by the body s eye alone, assisted as that may be by lenses yet to be introduced, at a knowledge of the molecular construction of this protean protoplasm, of the laws according to which it is built up, and the laws according to which it breaks down, for these laws when ascertained will clear up the mysteries of the protean work which the protoplasm does. And here we may venture to introduce a word of caution. We have, in speaking of protoplasm, used the words " con struction," " composition," " decomposition," and the like, as if protoplasm were a chemical substance. And it is a chemical substance in the sense that it arises out of the union or coincidence of certain factors, which can be resolved into what the chemists call " elements," and can be at any time by appropriate means broken up into the same factors, and indeed into chemical elements. This is not the place to enter into a discussion upon the nature of so-called chemical substances, or, what is the same thing, a discus sion concerning the nature of matter ; but we may venture to assert that the more these molecular problems of phy siology, with which we are now dealing, are studied the stronger becomes the conviction that the consideration of what we call " structure " and " composition " must, in har mony with the modern teachings of physics, be approached under the dominant conception of modes of motion. The physicists have been led to consider the qualities of things as expressions of internal movements ; even more impera tive does it seem to us that the biologist should regard the qualities (including structure and composition) of proto plasm as in like manner the expression of internal move ments. He may speak of protoplasm as a complex sub stance, but he must strive to realize that what he means by that is a complex whirl, an intricate dance, of which what he calls chemical composition, histological structure, and gross configuration are, so to speak, the figures ; to him the renewal of protoplasm is but the continuance of the dance, its functions and actions the transferences of figures. In so obscure a subject it is difficult to speak otherwise than by parables, and we may call to mind how easy it is to realize the comparison of the whole body of man to a fountain of water. As the figure of the fountain remains the same though fresh water is continually rising and falling, so the body seems the same though fresh food is always replacing the old man which in turn is always falling back to dust. And the conception which we are urging now is one which carries an analogous idea into the study of all the molecular phenomena of the body. We must not pursue the subject any further here, but we felt it necessary to introduce the caution concerning the word " substance," and we may repeat the assertion that it seems to us necessary for a satisfactory study of the problems on which we have been dwelling for the last few pages to keep clearly before the mind the conception that the phenomena
in question are the result not of properties of kinds of