not know just what occurs when the brain-substance is stimulated the results vary, sometimes directly and involuntarily following and corresponding to the cause, at other times, through the intervention of volition, either being entirely inhibited or so modified as to have no direct relation to the cause; (b) admitting a causal relation between sensation and the corresponding mental state does not prohibit this mental state from becoming itself a cause for any related thing that follows, for "an event which it takes previous events to produce, but which is itself unable to produce anything further, is something unheard of in the physical realm "-asking us to believe that our mental states are impotent as compared with physical events is in opposition to the fact that our volitions appear to us to be as capable of effecting physical results as is any mass of matter; (c) causation is probably something more than mere sequence, and, if so, that something more may in this case be conceived as connecting brain events with mental states-but, if causation is nothing but uniform sequence, then as pure sequence or causality may be assumed between volition and movement as between stimulus and sensation; (d) the impossibility of understanding just how a brainevent could create a mental state or ensure itself of being followed by a corresponding mental state, does not seem capable of demonstration by any automaton theory; (e) in the interaction theory these things are all explained by the presence of consciousness and volition as facts additional to the brain-process, whether we regard them as evolutionary products of physical sensation or as things entirely different which were implanted in the human germ from the beginning—whether, with Darwin, we assume that all adaptations of movement to sensation are the result of natural selection and the survival of the fit movement, or assume, with the Lamarckians, that they are to be explained by ancestral experience and hereditary transmission.

3. Parallelism denies all causal relation between the mind and the body, and maintains that the conscious brainevent and the volitional brain-event are both merely the result of the stored-up energy of the nerve-cells, the influences exerted through the blood, the currents from the periphery and from other centres, etc. Two main argu

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ments are used to prove this theory: (a) The argument from the principle of conservation of energy, which holds that, when we consider any material system of things in isolation from others, the amount of energy, potential as well as kinetic, contained in it is a constant quantity, and is neither increased nor diminished by any transactions between the parts of that system." And this is just as true of the physical world as a whole as it is of any part of it. If this assumption is true, manifestly, any possible physical action of mind is excluded, for the source of any energy is always to be found in the physical facts that precede the effect-neither the mind nor any other factor can be regarded as adding increment to the common store. This view implies that causation is mere sequence of single or combined forces and that all physical events are to be fully explained by physical causes. (b) The second argument for parallelism is contained in the nature of the causal relation, which the theory maintains “is of such nature that it cannot connect physical events with mental, or mental events with physical, but only events of the same ordereither two physical or (possibly) two mental events." The assumption here is that matter is not the sort of thing that can be acted upon by mind or anything else that might be assumed to have existence. In other words, the parallelists see an impassable gulf between mind and matter just as the automatists do. It is the gulf which the interactionists bridge by consciousness and volition,—that is, if we admit that it is a gulf at all. Doctor Strong says that parallelism is purely a metaphysical argument dependent upon our conception of the nature of mind and matter and that, as such, its validity rests solely upon the test of how well it accounts for or explains all related phenomena.

While the doctrine of conservation of energy seems reasonable and appeals to most thinkers, there are several respects in which its rigid interpretation is hard to harmonize with ideas that we feel to be correct. In the first place, by a change of direction or a different combination of the same energies we often greatly enhance their value. The same energy expended upon gold ore and iron ore produces radically different values. The energy represented by knowledge or skill we regard as of greater worth

in one case than in the other. This is also true of visible results. What we call efficiency is simply such a utilization of energies as produces the maximum result with the minimum expenditure of effort. The poorly constructed or poorly adapted machine is wasteful of energy and produces a result which is far less than its more perfect counterpart.. Nor can any inclusion of wasted energy satisfactorily explain that we do not have any more in one case than in the other. There is still a third way in which we find it difficult blindly to accept the theory. A change of direction or a variation in combination of energies often materially enhances the potential of the same substance and indeed of the same object. The same amount of energy expended upon turning a mass of iron into a multitude of needles gives it a far greater potential than if it were expended upon turning it into any single conceivable object. And the same energy expended upon making square needles instead of round pointed needles would lower the potential force of the energy. In brief, in our efforts to apply the doctrine of conservation of energy, we run across the same difficulty that we have in accounting for how it is possible to get mental results which intuitively we regard as of higher value, of greater efficiency, and of increased potential, from the mere nerve-stimulation produced by material substances and forces.

However, whichever theory we accept,-whether it be that of automatism, parallelism, or interaction,—the importance of the body cannot be greatly overestimated. If it is merely an automaton so fashioned as readily to respond in kind to the influence of substances and forces outside of itself, or if it is a mass of physical forces and materials so organized that it can wonderfully vary the direction and combination of the sum total of physical forces, the importance of so caring for it as to make it best fulfil its purpose still remains one of the most essential tasks of society. However, there are two great advantages for education in the interaction theory. These are, first, that it gives at least equal importance to the development and care of the mental attitude in regard to health as to the development and care of the body itself; and, second, it makes possible the more hopeful outlook contained in the idea that the

mind is superior to the body in its potential reach and, therefore, can be of the highest service in helping to care for the body. In other words, we may be greatly helped or hindered in our efforts in behalf of either personal or public health according as we accept or reject the idea of mind as a more or less distinct and potential force in human welfare.

The Changed Attitude toward Disease.

When Louis XV of France, during his last illness, was told by his physician, La Martiniere, that he had the smallpox, it is said that he made no reply but turned heavily in his bed, threw the coverlet over his face, and a little later said to his attendants, in a heart-broken tone, "I know now the state in which I am, and before long I shall be gathered to my fathers." The news of the nature of his illness soon decimated his court and caused most of his attendants to flee. And a few days later, powerful ruler as he was, he died almost alone from that which was then regarded as one of the most hopeless, as it certainly is one of the most loathsome, of all diseases. This was in 1774, and, although smallpox no longer arouses the terror and hopelessness it did in the days of Louis XV, there are still other diseases which even yet inspire in the minds of the people some of its helpless dread. But important influences have been at work, especially within the last few years, and a changed attitude in regard to disease is being effected. This changed attitude is especially noticeable as it reverses the former belief in the necessity and hopelessness of disease. This change of view is being effected by scientific investigation of the nature of disease, by improved curative measures, but more particularly through a change in the attitude concerning the functions of the physician.

Few realize the resources that are being expended upon the search for the causes of specific diseases, the methods of their transmission, and the means of their prevention, nor the sincere devotion and fearless self-sacrifice of the men who are at work upon these problems. The observation by Jenner in 1798 that most dairy-laborers were immune from smallpox, and his subsequent successful demonstration of

the theory that inoculation with the virus of cowpox is a preventive of this disease, may well be regarded as an accidental though exceedingly fortunate discovery. It was a case, however, in which a keen observer had the intelligence and energy to follow up his observation with persistent and careful demonstration. This was also true of the discovery of anesthetics, first publicly employed to produce unconsciousness to pain in 1846, a discovery which has so greatly enlarged the field of possible relief through surgery. But such random and unorganized effort cannot be relied upon for progress along any line of endeavor. Besides, where reliance must be placed solely upon observation, many erroneous and wholly unreliable conclusions naturally follow. True and economical progress demands investigation and demonstration that have the greater system and surety of science back of them. So generally did suppuration attend the healing of all wounds that observation had practically determined that it was a necessary attendant of all normal wound-healing. But, when Lister attacked the problem in a scientific way, he soon discovered that suppuration was merely the manifestation of the presence of germ poisoning in the wound, and that instead of furthering normal healing it greatly retarded it. Through careful experimentation he found antiseptics which would destroy these germs, cleanse the wound of their poisonous products, and rob surgery of its fevers and frequently fatal results a development which later on was to be followed by the discovery that by perfect cleanliness no germs need enter the wound, so that aseptic surgery has now replaced antiseptic surgery.

Lister's work marked the second great advance in surgery. But it also did more, for his discovery was based on a new method which was destined to revolutionize medical standards and practice everywhere. It was this new method to which Pasteur led the way in his great discovery that many of man's most serious ailments are due to minute invisible bodies which, under conditions favorable to their development, attack the tissues and tend to produce disease and death. Although Pasteur's first discoveries were made while investigating the cause of disease in grape-vines and later on in sheep, he was not long