534 "THE POPULAR SCIENCE MONTHLY. 



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 oxy- 

 gen of the atmosj)here 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 deli- 

 cate tissues of the brain. As the brain is the organ of the mind, it 

 is by and through the brain that w^e 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 circu- 

 lating through the brain in excess, are drowsiness, dizziness, dull head- 

 ache, an inability to fix the attention, a dislike for application, a weaken- 

 ing of the memory, and a general torpor of the intellectual jDowers. An 

 explanation of how and why these effects are produced would involve 

 certain principles of mental physiology a subject not within the scoj^e 

 of this paper. 



Special attention is requested to this statement by Dr. Routh:* 

 *' Experiment has shown that if an animal beke]3t 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 ex- 

 ercise 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 w^ho 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 re- 

 cover, at least for a time. 



The organic matters suspended in the air are derived (a) from the 

 body ; {h) from other sources. Epithelial cells or scales, very minute, 

 arise by desquamation from the external cutaneous surface, and also 

 from the mouth, j^harynx, 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' 



*" Infant Feeding," Part IV, chapter iv. 



