where they were most courteously received by Mr. W. MacLeod, curator, and Dr. F. S. Barbarin, assistant curator, who pointed out the many works of art in the building. After spending some time most pleasantly at the gallery, the line was again formed, and a visit was made to the Jefferson School-Building, where Professor Walter Smith, State-director of art-education in Massachusetts, addressed the teachers of the District of Columbia on the subject of " Drawing in public schools."

The large hall was filled with the teachers and their friends, who paid the closest attention to the professor's conversational explanations and blackboard-illustrations of the value and practical methods of teaching

drawing.

EVENING-SESSION.

The department assembled at 7 o'clock.

The PRESIDENT. It was considered important to have the subject of school-hygiene treated on this occasion by some one who could speak with authority, and accordingly we have invited the gentleman that I now have the honor of introducing to you, Dr. A. N. Bell, of New York, editor of The Sanitarian. [Applause.]

Dr. Bell said:

ADDRESS OF DR. A. N. BELL.

Mr. PRESIDENT, LADIES, AND GENTLEMEN: The paper which I have the honor of reading to you this evening is entitled

BRAIN-CULTURE IN RELATION TO THE SCHOOL-ROOM.

Education is a primary necessity of man. It is by education that the organs of the body acquire accuracy in their movements. The senses of sight, hearing, taste, and smell all learn to act. And the earliest charm of infant-life is to observe the progress of the education of the senses; to watch the study of a toy; to see the hands holding it at various distances, turning its different sides to view, tasting it, shaking it, and finally, when a little older, breaking it to see whence comes the noise. Who that has watched this process has not learned the first accomplishment of a teacher, to promote the education of the senses by the association of physical exercise, amusement, and study?

The passage from infancy to childhood is but an imperceptible step, marked by the continued expression of new experiences. Everything excites new impressions; everything must be examined with due deliberation; no hurry, no pressure, no fatigue. And during the while, ay, even during the whole period of waking hours, there is incessant motion. Nature has implanted in the young of all animals a pleasure in exercise. Muscular action being not only necessary for strengthening the muscles, but also the bones to which they are attached, the actions of crying and laughing, the deep inspirations of sobbing and joy, both alike tend to develop and strengthen the lungs. And the active exercise of the lungs promotes and develops the action of the heart, which, with increasing vigor, sends the blood to every part of the body. In all this the brain participates to an extraordinary degree, requiring that the young mind be exereised with the utmost care. By experience and habit the child acquires judgment, learns to compare one movement with another, to direct its organs to special objects, to produce this or that action, to take this or that attitude for the accomplishment of its purposes. And all the subsequent capacity of the brain will greatly depend upon the care with which it is cultured during the period of growth.

Imagination, perception, and memory-faculties which are always preceded and de

termined by the sensations-are all the subjects of education, enlarged and extended in proportion as new excitements and impressions call them forth and give them application.

"Glancing broadly at the whole range of psycho-physical phenomena," observes Dr. Tuke, "it is clear that it would be taking a very contracted view of the relation between mind and body, if we did not include in this relationship a reference to the inseparable nexus existing between the two, arising out of the fact that the organ of the mind is but the outgrowth and ultimate development of the tissues and organs of which the body itself is composed; that it not only unites them in one bond, but is, in truth, a microcosm of the whole."* Of all parts of the human body the brain is the last to gain maturity. According to Owen, "the brain has advanced to near its term of size at about ten years, but it does not usually obtain its full development till between twenty and thirty years of age." While the brain has not usually more than one-fortieth of the weight of the body, it receives about one-fifth of the whole volume of the blood. It is scarcely necessary to state in this connection that every organ and tissue of the body is nourished by the blood, and that upon the supply of it, and the condition of it, nutrition and development for weal or for woe depend. During the period of growth there is not only the development of new parts, but, in the brain especially, a change of structure going on until that degree of perfection has been attained which is necessary to the exercise of all the functions. Hence this period is characterized by extraordinary funetional activity in every part of the body. It is this which makes the demand for food so much greater during the period of growth than in after-years. Not, however, that the larger proportion of food in demand is wholly required as new material applied to actual increase, for that bears a very small proportion to the amount required for constant renewal which the increase involves, but the extraordinary functional activity in disposing of it and the corresponding necessity for replacing the waste in the buildingup and perfecting the structure according to the original plan. For it is characteristic of every living thing to follow out a certain inherent type or pattern, subject, of course, in some degree, to modification under the influence of external conditions, or, when these are aggravated, to acute disease and death; but such circumstances do not effect a permanent change in the original design. During the period of growth and change of structure the modifying influence of external conditions is most strongly marked. The constitution of the individual adapts itself to the circumstances and becomes fixed for the life-time. So that, if a child of originally healthy constitution be subject for any considerable length of time to such injurious physical conditions as produce a tendency to disease, unless the conditions are speedily changed, the effect is to establish a constitutional weakness or disease, not only during the life of the individual, but, it may be, a diathesis, with hereditary qualities for several generations. For, when the modification of the individual is once fixed in the growing brain, it becomes part of the general fabric; the different organs adapt themselves to the change and the condition is maintained by nutritive substitution. On the other hand, constitutional vices contracted during the period of growth may be gradually overcome in the progress of new generations, and, by a continued subjection to healthy surroundings, the normal type regained. It is apparent, therefore, that these changes of growth and structure are all affected by and through the circulation of the blood; its condition depends upon the air we breathe.

Air, everybody knows, is the absolute necessity of every living thing. It is the very first element of our bodily tissues, and breathing affords three-quarters of the nourishment of our bodies; and the other quarter, which we obtain in the form of solid and fluid aliment, is also in great part composed of oxygen, nitrogen, and carbonic acid-the elements of the atmosphere.

Chemically, the air consists of a mixture of two kinds of gases, oxygen, or vital air, * Influence of Mind upon the Body in Health and Disease. By Daniel Hack Tuke, M. D., M. R. C. P., p. 23; Philadelphia edition, 1873.

Anatomy of Vertebrates. By Richard Owen, F. R. S.; vol. iii, p. 144; London, 1868.

and nitrogen, in the proportion, by volume, of one-fifth of the former to four-fifths of the latter, and, besides these, carbonic acid, or fixed air, which exists in the free atmosphere in the proportion of about four parts to ten thousand.

In the small proportion in which carbonic acid exists in the free atmosphere it produces no evil effects; but in larger quantities it is not only dangerous, but frequently fatal. Being heavier than the other gases of the atmosphere, it is usually found in excess in low or confined places, such as mines, grottoes, and wells, and in the holds and steerages of ships, and in unventilated apartments generally. Under all such circumstances it is more or less dangerous to life. The bad air at the surface of close rooms is carbonic oxid, the product, usually, of burning gas and bad arrangements for warming. This, being the lightest of the deleterious gases, in close rooms rises to the surface.*

Pure oxygen will sustain life but a short time, owing to its stimulating qualities; it requires dilution, which seems to be the purpose of nitrogen, which cannot sustain life at all, and alone is deadly from its negative qualities. Carbonic acid pure is not respirable. If an attempt be made to inhale it, the glottis closes and prevents it from entering the lungs. When diluted with twice as much or more of air, it ceases to produce that effect upon the glottis, and is permitted to enter the lungs and the blood, and acts as a narcotic poison directly upon the brain. It is not possible to state how large a proportion of this gas may be present in the air without danger; it doubtless differs with different individuals. By experiments on animals it has been shown that an atmosphere containing 5 per cent. of carbonic acid is fatal in about thirty minutes.

Facts abundantly prove that respired air, or the air of occupied apartments containing of carbonic acid more than one volume per 1,000, is dangerous to health. Such air contains, besides the excess of carbonic acid, not infrequently the more deadly carbonic oxid, dead and decomposing animal matter, and other mephitic gases and exhalations arising from defective sewerage or vaults, but it is deficient in its very first life-sustaining property-oxygen-conditions predisposing to and frequently the cause of many fatal diseases.

The average amount of oxygen consumed by a healthy individual is half a cubic inch to every respiration, which in a day amounts to upwards of 25 cubic feet; and, as oxygen constitutes but one-fifth of the volume of the atmosphere, a single individual renders 125 cubic feet of air unfit for respiration every twenty-four hours by the abstraction of oxygen alone. Meanwhile there is exhaled by the lungs about 15 cubic feet of carbonic acid, 30 ounces of watery vapor, and an indefinite amount of organic matter, variously estimated at from 10 to 240 grains.

The whole quantity of air actually respired in twenty-four hours by a healthy person is about 400 cubic feet. This contains, when once passed through the lungs, 5 per cent. of carbonic acid, or more than one hundred times as much as it did when it entered them. It is plain, therefore, that in order to reduce respired air to the same standard of purity it had before it was respired, and to keep it so, the supply of fresh air must be at the least equal to one hundred times the volume of that which is thrown out, and upon this condition rests the importance of air-space, the space required depending upon circumstances. For various practical purposes the limits of space may vary from 300 to 4,000 cubic feet, the smallest proportion being the exaction for lodging-houses and the largest for hospitals, making due allowance in all cases for space occupied by furniture. And no deviation whatever should be made on account of children, whether in regard to the different members of a family or a school

room.

The smaller the space, the greater the necessity of, and the larger the opening required for, the admission of fresh air. If two or three hundred cubic feet only be allowed to the individual, the air must be changed every fifteen or twenty minutes, provision for which necessitates a draught and in cold weather great waste of heat. * Specific gravity: Oxygen, (unit,) 1,000; atmospheric air, in the aggregate, 1105.63; nitrogen, 971.37; carbonic acid, 1524.5; carbonic oxid, 971.2.-Graham.

41

Hence it is evident that the danger of "taking cold" in a small room, if it is kept ventilated, is much greater than it is in a large one. To reduce the gaseous components of respired air to their natural proportions and to neutralize its deleterious qualities, every person requires from 2,000 to 2,500 cubic feet of fresh air every hour.

To admit this amount of fresh air into a room is not as difficult as persons generally suppose. It has been calculated that with ordinary exposure an open space equal to five inches in the square will admit the passage of 2,000 cubic feet of air hourly; this, of course, implies that there should be an equal amount of open space for the escape of the air displaced. If, therefore, an ordinary window of three feet wide be open about an inch and a half at the top, and there be a chimney-flue in the room, the purpose is accomplished. Or the same by two windows on opposite sides of the room; or, it may be by crevices equal to this space about a door, in co-operation with one window. The multiplication of persons, it is plain, requires a corresponding multiplication of means.

In the aeration of the blood the organs of circulation and respiration are both no less essential to the maintenance of life than they are to each other. Their combined functions constitute the only means of admitting air into the body. And these functions must co-operate and be maintained, without intermission for one single minate, from birth until death. And yet, they have rest; the heart reposes about one-fourth of its time, and the lungs about one-third, but the periods of repose are too short to allow of any escape from a dangerous atmosphere.

The amount of blood in the human body constitutes about one-eighth of its entire weight, but it is variable within certain limits, depending upon the time and amount of food taken. Air is drawn into the lungs through the windpipe or trachea, which divides and subdivides into numerous smaller tubes leading to the air-cells, which, in the aggregate, constitute the lungs, situated one on each side of the chest and the heart between. The number of the air-cells has been estimated at seventeen millions, presenting a surface, if spread out, equal to about 22,000 square inches, or thirty times the surface of the whole body. The lining membrane of the air-cells, attenuated to the thinness of a cobweb, is the medium by which the air communicates with the blood. But the air in the lungs is not wholly changed with every breath. It cannot suddenly penetrate the membrane which separates it from actual contact with the blood and effect the required change in a moment. On the contrary, the air-cells are constantly full, the quantity contained being from 20 to 30 cubic inches, and of this the amount changed with each breath is only about one-tenth. Each fresh supply mixes with that which remains, and the change goes on incessautly, while that which is breathed out, although about the same in quantity, is, as already shown, very different in its properties. If the wall of an air-cell be examined with the microscope, it will be found to be covered with a net-work of exceedingly small blood-vessels, called capillaries, but much finer than hairs and so closely packed together that the interspaces are smaller than the vessels. These little vessels are the communicating extremities of larger ones, beginning and ending in the heart. At every beat of the heart, blood is sent into the pulmonary artery, and through it into the capillaries, where it is brought into contact with the lining membrane of the air-cells and through it exposed to the air; thence it returns again to the heart by the continuation of the capillaries into the pulmonary veins.

It is calculated that at each pulsation of the heart not less than one-twenty-seventh of all the blood in the body passes into the lungs; three times every minute the whole mass of blood is passed through the lungs and exposed to the air. Measured at each circuit, the whole quantity of blood so exposed in a day amounts to fifty-seven hogsheads, and, by weight, five hundred and forty pounds every hour, or twelve thousand nine hundred and sixty pounds in a day.

The quantity of fresh air imbibed by this exposure of the blood amounts to 616 cubie inches, or about two and a quarter gallons every minute, or upwards of two hogsheads pe: hour.

Life has often been compared to a burning flame, a sort of combustion, which, like fire, can never be sustained without the consumption of fuel, and, failing this, it flickers out, never again to be rekindled unless new life be given. The simile is in some respects marvelously perfect. Both flame and life depend upon air. Most persons have witnessed the experiment of placing a lighted candle or a taper under a bellglass, and know the result; that at first it burns brightly, gradually becomes feeble, and finally goes ont altogether. If instead of flame a bird or a mouse be placed under the glass, the effect on its life is precisely the same. In both cases the air is devitalized; it is not all used up, but that which is left will neither support a flame nor sustain life. A large proportion of the oxygen has been consumed and the proportion of carbonic acid and moisture increased. In the one case oxygen has been used to support combustion and in the other to sustain life; and air which has been respired, or in which anything has been burned, is always deficient in oxygen and contains an excess of carbonic acid and moisture. So far, then, as these conditions apply, every living animal represents combustion. In the free atmosphere, no creature ever suffered for the want of oxygen or from an excess of carbonic acid; but in crowded and unventilated rooms great harm often results from both.

Brain-culture is environed by the school-room. Upon the condition and management of the school-room depends the quality of the brain, and the brain is the soil of subsequent endowments. Education is the fruit; it contemplates a continuance of mental discipline and exertion far beyond the limits of the school-room or college-life. By education is acquired the mental and moral power to restrain the feelings, affections, propensities, and passions, so that none of these may ever gain the mastery over the intellect, a power which can never be acquired without proper brain-culture. A fruitful harvest can never come of an impoverished soil. Most of the anxieties and miseries of life result from the want of a sound and strong brain; and, as we trace back these to their source, they all seem to depend on the want of power to regulate impulse and feeling. A well-cultivated brain is unquestionably the true road to exalted virtues, and the union of a sound intellect and moral power the only stable foundation of true wisdom, by which health becomes, next to eternal salvation, the most important object of life.

A pure atmosphere is the first need of the school-room. Without it none of the vital functions can be sustained in health. We have seen the wonderful activity with which the functions of life are performed; that within twenty seconds a poisonous gas drawn in with the breath permeates every tissue of the body; that every single respiratory act multiplies the carbonic acid a hundredfold. No teacher, surely, will fail to appreciate the importance of these phenomena; nor should he fail to teach them to his pupils. A new series of questions in arithmetic should be devised for their inculcation, such as: If half a cubic inch of oxygen be consumed every respiration, how many respirations will it take to consume 25 cubic feet? If air that has been once passed through the lungs contains 5 per cent. of carbonic acid, how many volumes of atmosphere will it require to reduce it to four parts per ten thousand? If a single pupil breathes 70 cubic feet of air in four hours, how many cubic feet will be required for 600 pupils seven hours? If a closet of 300 cubic feet capacity requires 2,000 cubic feet of fresh air every hour to purify the air sufficiently for one individual, how many cubic feet of air will be required every hour to purify the atmosphere of a school-room 40 by 35 by 12 containing 75 pupils? Many other questions of similar practical utility will readily suggest themselves to the thoughtful teacher.

I cannot better close these remarks than by calling your attention to the recent action of the Rhode Island State Medical Society, as being eminently worthy of your serious consideration. This action may not meet with your approval in all its particulars, but it is commendable as being a practical and definite application of general principles and a suggestion to all thoughtful persons who are in any way responsible for the modes and methods of education:

"Whereas, although the present school-system has been brought to a high degree of