the human body precisely as in the use of the friction wheel or the voltaic battery, i.e., that eating and breathing are simply more refined forms of combustion and decomposition with which heat and motion are correlated. "All this points to the conclusion that the force we employ in muscular exertion is the force of burning fuel and not of creative will." "The body, in other words, falls into the category of machines.' "The matter of the human body is the same as that of the world without us, and here we find the forces of the body identical with those of inorganic nature. Just as little as the voltaic battery, is the human body a creator of force. It is an apparatus exquisite and effectual beyond all others in transforming and distributing the energy with which it is supplied, but it possesses no creative power." We have no disposition to dispute this. We concede that so far as the production of muscular power is concerned and its transmutation into heat, all this may be true. We question very much, indeed, whether the experiments have been conducted with mathematical exactness, or whether the laws have been formulated with scientific precision or, as Tyndall phrases it, whether" the interdependence" between the several factors has become quantitative-expressible by numbers." But making nothing of this, and conceding that the law of conservation and correlation of muscular force operates as Prof. Tyndall contends, we cannot but inquire whether the human body performs no other offices than these two, i.e.,whether all the functions of life are resolvable into digestion, breathing, walking, climbing, and lifting weights? Prof. Tyndall himself, it would seem, more than half suspects that his machine does something more than transmute force by eating and breathing. When he says: "Thus far every action of the organism belongs to the domain either of physics or chemistry," he bethinks himself that the nerves have something to do with the application and direction of force, if not with its generation. These are sensor and motor. But these do not create force-they do not originate energy-they simply direct it, "as Mayer says, with admirable lucidity, as an engineer by the motion of his finger in opening a valve, or loosening a detent can liberate an amount of mechanical energy almost infinite, compared with its exciting cause, so the nerves acting on the muscles can unlock an amount of power out of all proportion to the work done by the nerves themselves. The nerves, according to Mayer, pull the trigger, but the gunpowder which they ignite is stored in the muscles. This is the view now universally entertained." We pass over the concession that has inadvertently dropped from the lips of our author, that work of some sort is done by the nerves themselves, which he had not noticed, and

certainly had not shown to be the accumulation or transmission of some occult transformation of heat. We simply observe that according to Tyndall and Mayer and all the scientific world, a special function is accorded to the nerves-over and above any which the correlation of forces can illustrate, under mechanical law in the machine or chemical decomposition in the battery and this is a function of directing-i.c. of liberating and detaining muscular force-which is illustrated by lifting a valve, or pulling a trigger. It were far better illustrated, as it seems to our unsophisticated minds, by the power of a band or gearing to carry motion in a machine, or of wire to transfer potential motion or potential heat in a battery. It is very evident that when Prof. Tyndall began his argument which was to prove that "the body falls under the category of machines," and that as a machine it generates no force, he does not seem to have thought of any other function as possible except the two, of generating or transforming force. Not seeing that his animal body, his homme machine, does through the nerves perform the additional function of directing or transferring force, that is of determining when and where it should act, it is not surprising that he meets this indefinitely conceived demand by the convenient image or picture of a valve, a detent in a machine or a trigger in a musket. He ought to have bethought himself, and corrected the premises of his disjunctive, and instead of asserting, the animal body either creates force or transforms force, he should have said, the human body either creates force or transforms force or also directs force. Then in order to prove that it is a machine, he must prove that it directs force through the nerves, by either mechanical or chemical agency. This last he does not attempt to do. He does indeed assume that nerve substance is wasted by use, and implies that heat is probably evolved in nerve activity, and illustrates this by a rod of antimony rendered sensitive by electrolysis as it carries forward heat and smoke from one end to another. From this he would doubtless leave us to infer that the nerves like the muscles never act, except under the general conditions of correlation. But in all this there is not the slightest attempt to explain by what mechanical process the nerves direct or transfer motion. He does indeed tell a somewhat long story about experiments which show that the process of movement or affection in the nerves, sensor and motor, to and from the brain, requires an appreciable lapse of time, so that a second must elapse before. a whale seventy feet long would feel a wound in his tail, but he is sublimely unconscious of the fact that the new function of shifting motion, by valve, detent, or trigger during this second, makes the machine a little more complicated than he had at

first supposed. But this slight difficulty not having occurred to him, the animal body is accepted as a finished machine, which is now ready for the "kindling of consciousness," which he confidently anticipates may turn out to be a more refined form of heat evolved by mechanical laws. With this impression, he marches boldly up to the new line of inquiry, which relates to the connection between this machine and a highly poetical or idealized force, sometimes called the soul. To say nothing of these little difficulties, which have hindered us from going forward with him at the rapid pace which he has assumed, there are others which compel us still to follow him haud passibus æquis. We are not satisfied that he has disposed of sundry other questions which may be asked in respect to the "animal body." Conceding that in breathing and eating and muscular action, this body is a machine or a voltaic battery, and not insisting on the peculiarity of the function by which the nerves transfer or liberate motion, which Prof. Tyndall has scarcely recognized and imperfectly explained, we hold that this body performs other functions, which the doctrine of the conservation of force does not at all account for, and which are not proved to be mechanical by Prof. Tyndall's argument, or the analogies which it suggests. We need only refer to these. This body grows by a peculiar method, through cellular accession from within, from living food, making thereby new and peculiar tissues in great variety. Many of these tissues become organs which are capable of secreting special fluids or substances, which themselves pass by an orderly succession into the various permanent substances of the body. Each organ secretes that which finally returns to itself, increasing its bulk, following its form, and fitting for its function. These parts grow after a plan, which is general in likeness of form, size, and symmetry, so far as it is common to all living bodies, special so far as it is peculiar to each species, and individual so far as it is fitted to each individual. Not any one of these effects has ever been accounted for by the joint operation of any known mechanical or chemical laws, much less by their sole or separate activity; least of all with the slightest approximation to that mathematical rigour which Prof. Tyndall contends is the indispensable requisite of scientific certainty. All that can be said has been said by Prof. Tyndall, that so far as heat and muscular activity are concerned, there is probable correlation between the two-that in living matter as truly as in inorganic matter, the combinations in growth and the decompositions of waste are chemical in their ingredients and chemical in their relations. This is not surprising-did not the living body consist of materials which obey mechanical and chemical

laws, this body would so far not be material. This is not at all in question, and so far as a correct conception of an animal body is concerned, it is superfluous to argue the point. What is in question is whether this body is capable of no other functions than these, not whether it is a machine or a voltaic battery, but whether it is not something more. The question. is not whether so far as it is material it is subject to material laws, but whether it is not also a living body, and what forces, relations, and laws this conception implies.*

What is most surprising is, not that a certain class of scientific men do not see this distinction, but that so many insist in one breath that no scientific theory can be accepted which is incapable of mathematical formulization and experimental verification, and in the next breath adopt a theory of life on a mechanical and chemical basis, the laws of which they do not profess to have formulated in numbers, nor to have tested the alleged facts by experiment. Prof. Tyndall insists that "the interdependence of our day has become quantitative-expressible by numbers"—and that where law cannot be formulated by numbers there is no science. We insist that if under this definition, Psychology, Morals, and Theology are excluded from the domain of science, Physiology should be excluded also, and yet the whole doctrine of development, with heredity and its variations and integrations, and all the nomenclature by which the soul is demonstrated to be but a higher potency of matter, and personality to be an ideal fiction, and God an entirely superfluous hypothesis-is derived from the very operations of life, scarcely a single one of which if tried by the criterion in question has been scientifically fixed or formulated.†

*Since writing the above, we happened to open the often-read discourse of Du Bois Reymond, of Aug. 14, 1872, on the limits of the knowledge of nature. On page 26, speaking of a supposed ideal knowledge of the physiological processes, analogous to our actual knowledge of astronomical movements and laws, he says:-In that case, "muscular contraction; glandular secretion; electrical pulsation; optical illumination; ciliary movement; the growth and chemism of plant-cells; the impregnation and development of the egg; all these now hopelessly dark processes would then be as transparent as the movements of the planets." It would seem that these processes are no longer dark to Prof. Tyndall's illuminated vision.

† Prof. Tyndall asserts, not infrequently, with unqualified positiveness, that sciences cease where mechanical relations cannot be mathematically determined. He objects to any scientific recognition of the phenomena of spirit, in such language as this "If we are true to these canons we must deny to subjective phenomena all influence on physical processes. Observation proves that they interact, but in passing from the one to the other we meet a blank, which mechanical deduction cannot fill." He seems to over

But leaving this consideration and conceding for the moment all that Prof. Tyndall violently and unscientifically assumes, viz.: that the animal body is a machine-let us follow him up to the line where its supposed relations to the soul begin. We accept the case suggested by himself: "An aerial wave, the energy of which would not reach a minute fraction of that necessary to raise the thousandth of a grain through the thousandth of an inch, can throw the human frame into a powerful mechanical spasm followed by violent respiration and palpitation." We give the illustration which he quotes from Lange. A merchant sits quietly in his chair-he reads a letter, it makes him spring to his feet, he calls his carriage, gives orders in haste to all his clerks and servants-rushes on Change, buys, and sells, and signs a few papers, and in a half-hour has saved his fortune from wreck; he comes back, and throwing himself into his chair says, now I can breathe.' "This complex mass of action, emotional, intellectual, and mechanical, is evoked by the impact upon the retina of the infinitesimal waves of light coming from a few pencil marks on a bit of paper." "What caused the merchant to spring out of his chair? The contraction of his muscles. What made his muscles contract? An impulse of the nerves which lifted the proper latch and liberated the muscular power. Whence this impulse? From the centre of the nervous system. But bow did it originate there? This is the critical question." It is indeed the critical question. And how does Prof. Tyndall answer it? We should first inquire, how does he ask it? for it is important to notice that as with lawyers so with philosophers it often happens that the way in which they phrase their questions reveals the answers which they expect or desire, and in some sort compel. Prof. Tyndall does not deny that other phenomena come in beside those of the ordinary nervous, digestive, and breathing mechanism. He admits that terror and hope, sensation and calculation, with possible ruin, all succeed one another between the impact on the retina and the lifting the latch which releases the reaction that proceeds from the centre of the nervous system. But he assumes that whatever is the nature

look the fact, that tried by this test, physiology itself, as conceived by the great majority of its devotees, is as little a science as psychology. His own conjectures that the animal body is a machine, are as far from any mathematical formulization as the not dissimilar theory of Descartes. The psychological theories of the school of Herbart are more solidly and consistently mathematical than are the headlong guesses of Prof. Tyndall's physiology. Tried by Tyndall's test, the new chemistry is also in some danger of being pronounced unscientific. See Du Bois Reymond.-Ueber die Grenzen des Naturerkennens, pp. 4, 5.