Page:Popular Science Monthly Volume 19.djvu/550

534 If ample provision is not made for the removal of the vitiated air, the proportion of carbonic-acid gas continues to increase; and, as it is much heavier than air, the density becomes greater. Now, this increase of the air's density interferes with and retards the diffusion between the impure gases held in solution in the blood and the oxygen of the atmosphere—in other words, interferes with respiration. The consequence is, that the blood is not purified of the carbonic-acid gas which it holds in solution and combination. Not being removed as fast as it is formed in the body, it accumulates in the blood; the blood carries it throughout the system, circulating it through the delicate tissues of the brain. As the brain is the organ of the mind, it is by and through the brain that we think, reason, memorize, learn. For its healthy and vigorous action, a full supply of pure blood is an imperious necessity. The effects produced by this gas, when circulating through the brain in excess, are drowsiness, dizziness, dull headache, an inability to fix the attention, a dislike for application, a weakening of the memory, and a general torpor of the intellectual powers. An explanation of how and why these effects are produced would involve certain principles of mental physiology—a subject not within the scope of this paper.

Special attention is requested to this statement by Dr. Routh: "Experiment has shown that if an animal be kept confined in a narrow, closed apartment, so that the air supplied is always more or less vitiated by the carbonic acid which it expires, however well fed that animal may be, tubercle (consumption) will be developed in about three months." If this be the case, a large percentage of cases of consumption should be met with among the inmates of badly ventilated schools. But, fortunately, the disease is comparatively infrequent under the age of fifteen, and added to this is the protecting influence of the active exercise in the open air usually indulged in by school-children. It is upon the teachers that its blighting effects are most apparent, as they are predisposed by age, they neglect exercise in the open air, and their mental labor is severe, and worry of mind exhausting. Of eleven teachers who died during the last eight years within the limits of one county in Pennsylvania, two died of acute disease, one of an overdose of an habitual narcotic, and of nine attacked by consumption, eight died—six ladies and one gentleman; the other, a gentleman, will recover, at least for a time.

The organic matters suspended in the air are derived (a) from the body; (b) from other sources. Epithelial cells or scales, very minute, arise by desquamation from the external cutaneous surface, and also from the mouth, pharynx, and bronchi. Being exceedingly light, they float in the air, and are inhaled, lodging in the throat, trachea, and even deep in the lungs. It is not pleasant to contemplate the fact that