quantity of free ozone in the air may induce nasal catarrh, bronchitis, and asthma by the constant irritating of the mucous surfaces with which it comes in contact.

With reference to the anthropotoxins (the organic matters) exhaled in respiration, Brown-Sequard, Billings, Mitchell, and others have given us some definite experimental data upon which to base a conclusion. When expired air is condensed and liquefied, there results a clear, odorless liquid which contains only a trace of organic matter. Its effect on guinea-pigs and human beings when taken internally or injected into the blood is found to be wholly indifferent and harmless. Other experiments in which mice were compelled to breath the expired air, each of the other, when other conditions were normalized also gave negative results. The conclusion is thus forced upon one that other factors than deficient oxygen, excess of CO2, or the presence of anthropotoxins are responsible for the devitalization of indoor air.

Of late there is a disposition to attribute the stuffiness and deadness of air in heated schoolrooms and dwellings to its lack of moisture, its low relative humidity as compared with the out-of-door air. In the lake region in which Chicago is located the average outside humidity is in the neighborhood of 72 per cent, varying greatly, to be sure, from day to day, with fluctuations in temperature. In artificially heated rooms (schoolhouses, factories, and dwellings) the average relative humidity rarely exceeds 30 per cent. In Nebraska the relative humidity of artificially heated rooms seldom gets as high as 20 per cent for the winter months. These differences between the moisture indoors and out of doors are striking, but outof-door variations are often quite as pronounced. Along the California coast, day after day, the average relative humidity may approach 100 per cent at dawn and fall to 22 per cent at noon. At Denver the out-of-door mean relative humidity for the entire year is only 42 per cent.

Attempts have been made to overcome the great differences between out-of-door and indoor relative humidity by a process of humidifying the air, and if we are to believe reports the results have been gratifyingly satisfactory. The air in the American Bell Telephone Building at Boston is kept at a relative humidity of 50 per cent by injecting into the entering hotair current a jet of steam; 675 gallons of water (twenty-two barrels) in the form of steam is required for this purpose every ten hours. The practice of humidifying the air was followed also in one of the Chicago school buildings, but the results were not accurately tabulated, so it is impossible to state just how much the air was humidified. A few years ago some careful experiments on humidifying air were made by Professor Loveland at the University of Nebraska. These covered thirty days. Two seven-room houses, alike in construction and each heated by a hot-air furnace of the same make, were selected for experimentation. It was found that to raise the relative humidity of one 10 per cent above the other, as indicated

by the hygrometer-i.e., from 20 per cent to 30 per cent-it was necessary to evaporate sixty-four gallons of water daily. It was further demonstrated that the ordinary furnace or radiator pan, or vessels of water placed about rooms, affect the humidity so little that it is not registered by the hygrometer, which means the influence is less than a fraction of one per cent. Most persons will testify to feeling a considerable difference in the character of the air as a result of such evaporating devices, but the difference is unquestionably psychological rather than physical.

At the Boston Telephone Building it is asserted the rooms are as comfortable with a temperature of sixty-nine degrees Fahrenheit, relative humidity 50 per cent, as they formerly were at seventy degrees Fahrenheit and the drier air. The relation between dry or humidified air and bodily comfort is by no means a simple one. To determine exactly what this relation is requires a finer and more discriminating line of experimentation than has yet been undertaken. We know, for example, that a temperature of eighty to eighty-five degrees Fahrenheit with a high relative humidity is more oppressive than a temperature of ninety degrees Fahrenheit with a very low relative humidity. But what are the physiological effects of high and low humidity in temperatures ranging from sixty to seventy-two degrees Fahrenheit we know little or nothing definite. After all, it is not the relative humidity of the air which is significant in affecting vital processes so much as the air's thirst or drying power. Thus air at fifty degrees Fahrenheit with a relative humidity of 36 per cent and air with a temperature of eighty-six degrees Fahrenheit and relative humidity of 80 per cent have exactly the same drying power. That is, to become completely saturated, each requires the same quantity of watery vapor per unit volume. A cubic foot of air at fifty degrees Fahrenheit, relative humidity 36 per cent, and a cubic foot of air at eighty-six degrees Fahrenheit, relative humidity 80 per cent, will each absorb .0,003,756 pounds of water, and hence the effect on the mucous tissues of the nose, throat, and lungs ought to be the same, altho a relative humidity of 80 per cent, eighty-six degrees Fahrenheit, is considered high, while a relative humidity of 36 per cent is thought of as very low, when dissociated from the temperature of the air. Arid climates are generally not thought of as being particularly conducive to catarrhal affections. Neither do the wide ranges in humidity experienced along the California coast during the course of each day seem to be particularly unhealthful. Places of low relative humidity indeed appear to be famous as health retreats for those afflicted with bronchial and lung troubles. In truth, the humidity factor is still very largely an undetermined one, and before one can become assertive more will have to be learned as to how it affects physiological functions, and that under careful experimental conditions. Whether a room not heated beyond sixty to sixty-eight degrees Fahrenheit, with a relative humidity of 60 per cent, or 70 per cent, is as comfortable as one heated to seventy-two degrees Fahrenheit, relative humidity 40 per

cent is also still problematical. Dr. Hill claimed to have gotten very good results with a schoolroom temperature of fifty-seven to sixty degrees, relative humidity 70 per cent. German and English homes, moreover, are rarely heated above sixty-nine degrees Fahrenheit, but these peoples have accustomed themselves to a lower temperature. They are healthy, but whether under our different climatic conditions this would be true generally remains yet to be determined. In Germany and England sudden wide fluctuations in out-of-door temperatures do not occur. Rises and falls in temperature from twenty degrees to forty degrees Fahrenheit do not occur within the space of a few hours, as is common in the lake states, and their human organisms are not subjected to the strain of sudden adaptations to the changes they are unprepared for as are ours. These sudden adaptations and other factors yet to be determined must be reckoned with in a consideration of the optimum condition of the air for good health. Three factors conditioning the results obtained in openair and low-temperature rooms have yet to be considered: (a) the influence of a small class enrollment; (b) the period of complete relaxation and rest in the middle of the day, and (c) that of wholesome food and proper habits of eating.

Inasmuch as the open-air rooms look to the improved health rather than to a bettering of the scholarship of the children, a general freedom and feeling of lack of restraint was encouraged. This is possible with an enrollment as small as twenty-five, whereas it offers a problem far more complicated when a teacher has larger numbers to handle. The children were encouraged to be happy, to forget their afflictions and the handicaps which caused them to fall behind in their classwork. The emotional reactions were striking. Truant habits were broken up, the aforetime helplessness and mental indifference disappeared, and a consequent alertness and spontaneous interest in the routine of the school work developed. Not the small enrollment, to be sure, nor any other one factor alone was responsible for this change. It is more probable that each contributed its share, of which the part due to the small enrollment unquestionably was not insignificant.

It seems like indulging in platitudes to mention the rôle played by the factor of wholesome food. Many of the children coming to the rooms were injudiciously fed, and nearly all underfed. So weak, anæmic, and impoverished were their little bodies that even a modicum of mental vigor was altogether impossible. With the increased metabolism and the building up of their physical organisms there followed, very obviously, an acceleration in the mental responsiveness, which in the absence of all other factors would of course have been clearly manifest.

The importance of the last factor, that of complete relaxation and rest, is not often considered. Its significance, too, it is to be feared, is altogether too lightly held. During the past two or three decades a not inconsider

able number of studies have been made of school children, all pointing to the fact that the curve of fatigue during the school day runs astonishingly high. The reaction of the results of these fatigue studies has been in the direction of a rearrangement of the daily program, so as to put difficult and taxing studies at those hours when the fatigue curves were least manifest and to fill in the periods of high fatigue with recreation exercises. The advisability of allowing the children opportunity for complete relaxation, sound sleep, with a lowering of the pulse rate, a slowing down of respiration, a diminished metabolism, and a consequent recuperation of the nerve centers, had not received notice until put into practice by those dealing with children of low vitality and physical depletion-those with tubercular and anæmic tendencies.

The effect of this daily siesta in the way of enhancing the children's physical vigor and developing an increased mental alertness and plasticity, it is perfectly logical to believe, must be very striking. It doubtless contributed no small part toward developing more efficient school reactions on the part of the children in the open-air and low-temperature rooms.

Chicago's experiment with this special class of schoolrooms has been too brief for us to become dogmatic. Yet some results which are fairly astounding have been attained. It is really unfortunate that it is impossible to isolate, differentiate, and assign the proper weights to the several factors responsible for them. On the mental side alone, children who had shown three and four years of retardation in their studies were able to complete the school work of one and a-half, and in four instances of two, grades in a single year. The truant records which followed many of the children of the schools disappeared. The discipline cases vanished, and the forcing process on the part of the teacher was displaced by a wholesome individual initiative and interest. The maximum number of taps that could be made in a minute's time with tapping device, in the course of three months, increased from 4 per cent in some cases to 23 per cent in others. There was observed an increased adaptability, a greater resourcefulness, a keener insight in the unraveling of puzzling situations, and appreciable development in persistence and tenacity in solving difficult and complex problems.

The fruits which the open-air and low-temperature rooms have yielded are well worth the financial outlay entailed, when the heightened physical and mental efficiency of the children, who were enrolled, are taken into account. A large percentage of the two hundred odd children who were given these special advantages would otherwise unquestionably have succumbed as a result of the deadly inroads of tuberculosis, and the economic loss resulting from the death or the physical and mental impairment of a growing individual is easily reckoned. In the aggregate the economic waste, aside from humanitarian considerations, would have been tremendous. As it stands, the children have been developed into producers, and thus

thru their contributions to society will far more than remunerate it for the additional expense incurred in a few months of their special education.

The possibilities, however, of making such school advantages as obtain in the open-air rooms more universal, rest largely upon financial grounds. The increased per-capita cost incident to maintaining such schools is of course prohibitive when considered in the large, and until some means for obtaining school revenues not now available is at hand, open-air rooms will have to be limited to those children whose health is in peril. They will have to be considered in the light of instrumentalities for recovering those who have gotten beyond the reach of the ordinary school and health agencies.

But the experiment of the open-air and low-temperature rooms has had a wider import. As in the case of most activities for the amelioration of the condition of the unfortunates, there has resulted a reflex effect upon the habits and methods of ministering to the needs of normal individuals. Were no other effect manifest, the reaction which open-air rooms have had in directing attention to the proper ventilation of schoolhouses, dwellings, and factories, to directing attention to the need for pure air—as near outof-door air as possible on the part of all individuals, would be abundantly worth the effort and expense entailed. Only recently and all unconsciously has the human been making the transition from an out-of-door to an indoor dwelling animal and it always requires a rather intense agitation to bring to an individual's consciousness the necessity for modifying the conditions of his habitat so as to make his readjustment to a new order of life safe and wholesome. Such the focus of attention upon open-air schoolrooms, it is hoped, has accomplished.

OPEN-AIR SCHOOLS

LEONARD P. AYRES, RUSSELL SAGE FOUNDATION, NEW YORK, N.Y. The report of the recent United States Census will tell us that the greatest industry in San Francisco is that of trade, in which some twelve thousand merchants and dealers are engaged. It will further tell us that the greatest sedentary class in this city is that made up of clerks and copyists, including a total of some nine thousand people. Altho these will be the official figures, they will be wrong; for the greatest industry in San Francisco is not trade, but education; and the greatest sedentary class is not made up of the clerks and copyists, but rather of the fifty-five thou sand people engaged in teaching and being taught in the public and private schools.

A similar condition exists in every city thruout the land. Everywhere the largest as well as the oldest organized industry is education, and everywhere the greatest sedentary class is made up of our school children. It is only within the last few years that schoolmen have begun to ask what