standard. Of course it is now known that the "oxygen saturation" of the blood under usual conditions of indoor ventilation is not a little below the amount of oxygen required for the best "physical" exertion. Here, as perhaps likewise in the proteid allowance of Chittenden, the real human need is for a very wide margin of safety, and here as is not the case with the trust-supplied ox meat, the supply of atmosphere is riotously abundant and cheap, praise God for that-"it is only the heavens that are given away." Third, the accumulation of anabolic materials in the musculature, with its probable consequent over-stimulation of the vastly numerous and delicate kinesthetic sense organs, and through them of the whole nervous system. Fourth, the under-stimulation of the blood-lymph circulation, especially of its vasomotor functions. Fifth, the last element of school fatigue we need to discuss, the undoubtedly still too common eye strain. Our present problem is not the psycho-physiology of these conditioners and elements of fatigue (although much of both theoretic and practical interest lies therein), but rather to inquire as to a practical means of their decrease or avoidance. In general, hygiene in the public schools is usually not thoroughly taught by that regard to practical demonstration and training in it that the wide importance of its subject-matter demands. The present is no proper occasion perhaps to express an opinion as to several factors of what in the schools doubtless is supposed to be scientific hygiene, but nevertheless it is patent to many physiologists and physicians, at least, that much of the material in the elementary text-books of hygiene is an outworn relic of the more or less distant and surely superstitious and dogmatic past. R. C. Cabot has exploited this matter interestingly already. But such as it is even, school hygiene is taught too didactically and far too little by example and forced training. To the average child of ten or seven ordinary instruction in this subject rarely becomes a matter of the necessary interest, and even more rarely still does it acquire for him, ever, that vital importance that the statistics of nervous diseases, of tuberculosis, or of arteriosclerosis, for example, so strongly impress upon the wide-reading physician. Statistics would scarcely be proper food for the average girl of ten or even for the boy of twelve! but there may be sometime found a way of teaching hygiene that perhaps in time might wholly do away with such statistics for even the ever-hungry physician to devour-namely by the proper training of school children in addition to the instruction by precept and daily printed lessons in an often state-ruled text-book. Years of actual experience with its applications during childhood would make hygiene into something real and vital,-a rule of happy and long life, a living subject to be appreciated and lived by, and in turn - taught to the next generation by the children of this. In fine, its importance demands that hygiene be taught to our future citizens practically and in such a way that it shall take its proper place in the public mind as a most fundamental and indispensable part of the common knowledge as to how to live. The money value of health and of general efficiency based on health is a sort of appeal that has never received its due consideration in teaching the multitude how to live well. This fact is the more strange because it would almost seem that no appeal that could be made to the majority would "strike in" more deeply. The anti-tuberculosis campaign has well started a common knowledge of the economic value of a life, but the principle needs extension into the broader and surely not less important range of general, sexual, and personal hygiene. This is more than a matter of impersonal political economy that in the hidden pages of a book seeks the greatest good of the greatest number, for it concerns, and of course in a vitally personal way, every family head, as well as every individual whatever who has dependents, or who is dependent on the earning powers of another. A scientifically sound knowledge of hygiene and of prophylaxis is obviously a large part of the personal capital for this excellent investment in long life. The insurance companies and the tuberculosis societies have the data-why are they not taught in some impressively interesting form to the children and (by other means) to the men and women of our land? Who uses most of the medical school buildings in the evening? With no intention of enlisting in the ranks of patent medicine makers in offering a panacea for the ills of public elementary school hygiene (not as a subject now, but as a condition) there is one expedient which might go far, further than appears, perhaps, at first sight, to accomplish several things at once in the direction of improvement. (The apparent reasons for making this pretension will be found below.) The formula is simple, and the materials at hand in every indoor schoolroom in the world: Systematically and continually open wide the windows for five minutes or so every half hour whatever the weather, and require the children to practice during that time marching, gymnastics, etc., carefully adapted to the temperature outside and to the age of the pupils. This practice of course in principle, is in vogue in many schools (e. g. those of New York City), but not on the efficient scale, with the system or with the effects probably that are here contemplated and proposed. The present intent is to suggest its vigorous performance as a routine part of the regimen throughout every school day in the year, as a part of the pupils' training, and with the same enthusiasm and intelligence and originality that the really good teacher displays in other respects. Let us look at some of the results that might reasonably be expected from the action of such a system, and note its probable advantages, as well as discuss objections that might be made to it by some of the parents and teachers. It is too often forgotten that the human brain developed from the brute brain largely as an organ of motor co-ordination and control, and not as an organ of "mind" in the still too frequent narrow use of that term. Another circumstance besides is still too frequently ignored by pedagogues, namely, the inherent impulse to activity that is at the very foundation of child life. On these two basal biologic principles depend the educational doctrine of attention. But attention is in its nature inhibitory primarily, inhibitory of distractions, and therefore in a sense is unnatural except in its reflex or "passive" form determined by interest. The outcome of these theoretic facts is that young children should not be expected to attend for more than a short period at a time to anything that does not itself impel attention. An hour is certainly far too long for any school exercise for a child (and too long for the average college student). It is only at a prodigious actual waste of nerve energy that a boy or girl is compelled to "attend" as long as this. In practice they do not really attend more than half an hour, however close the appearance of it; meanwhile the mind does not learn, and in fact tends to become lethargic, and besides to acquire the habit of inattention. This then is one general reason why the fresh air and the exercise of the proposed plan would be a benefit—it would keep body and mind, in short the attention, widely and more interestedly awake.* From another point of view half-hourly open windows and light bodily exercise would go far toward preventing that psychophysical school fatigue that we have set forth already, and mainly for the following physiologic reasons: In the first place that, perhaps katabolic, fatigue of the individual neurones of the nerve masses of which we spoke would at least be lessened by thus giving them a larger nutrition supply and exhaust, so to say. The cerebral circulation would be hastened, and the katabolic waste from the chromatin masses of the brain cells would be more rapidly taken away by this frequent acceleration of the lymph, for the latter would then osmose through the capillaries and thence soak through the neural tissues faster. In the second place, a really abundant and truly adequate ventilation would be afforded by the plan, and it is not easy to see how else such a valuable approximation to staying out of doors could be secured. The normally ceaseless and inherent movement of ameba wholly stops after the animal has been placed about an hour in water containing no free oxygen. The human nervous system especially seems to be dependent for normally unfatigued activity on an abundance of this vital gas. Into the chemical details of this matter we do not need to go, and it is necessary for emphasis only to refer to the difference of mental sprightliness of persons in an ill-ventilated room and when in the open air. Again, practically, the large saving of money by any method of school construction that would avoid the highly expensive installation and running of ventilating apparatus would be See a series of six articles on the physiology of attention to be published by the writer in the American Physical Education Review during the coming winter, 1910-II. surely a matter of great importance,-thousands of dollars, at least, annually, in any considerable and in any growing city would be saved-perhaps, indeed, enough to build the much desired but expensive "new schoolhouse"! This financial phase of the problem should appeal especially to rapidly growing cities, for through the open windows of the future schoolrooms, multiplying so fast, would come unlimited normal out-door air into every school building, however elaborate, at no expense. A third and much disturbing manifestation of school fatigue is what every one is familiar with as "the fidgets." One sees it in young children especially, but many active adults, even, whenever the convenient excuse offers and they fail to go to church, are apt to experience this unpleasant condition toward Sunday evening! Its chief physiologic cause has already been implied at least. Its invariable and easy relief is to be readily had by muscular exertion especially of a sort that exercises a large mass of the musculature, and notably soon, as all persons are aware, by walking in the open air. Here properly to be complete our discussion should include the whole important and basal relationship between muscular innervation and the mental process. Suffice it to say, however, that they are of course inter-dependent, and that the continual irritation of the cord and brain in this fidgety state precludes all excellent mental effort, and makes remembering nearly impossible. On the other hand frequent and widespread muscular exertion, such as proper marching, frees the muscles (half the mass of the body, be it remembered) of their over-accumulated impulse to constant activity, and relieves the central nervous system of the abnormally strong kinesthetic stimuli coming from them. The ordinary one-piece recess is obviously not adequate to prevent in young pupils this common hygienic defect of the schools. This is one of the most conspicuous elements of "fatigue." A fourth, and it may well be the most important factor perhaps of school fatigue, comes from what we may call some degree of circulatory, and particularly vasomotor, stasis. This involves importantly the decrease of lymphatic tissue flushing that has been already referred to. The vasomotor and general hydraulic mechanism of the brain is undoubtedly one of the most |