8 Cincinnati Society of Natural History. 



element of our being, the ox^'gen of the external air, from 

 our houses, and substitute its toxic element, carbonic-acid 

 gas, thus neutralizing to some extent the vital necessities of 

 our existence. It is scarcely too much exaggeration to saj^ 

 that the worst outside air is better than the best inside air. 

 If the results are not rapidly explosive in appearance they 

 are certainly devitalizing in results. Altitude may diminish 

 the absolute or relative amount of oxygen in mountain 

 resorts, but there is compensation in the increased amount of 

 respirator)' movements, and in the otherwise greater purity 

 of air. 



Any obstruction to the entrance of the proper amount of 

 oxygen into the lungs is liable to modif}' the whole series of 

 nutritive processes going on in the tissues of the body. 

 Correlated with oxygen we mention ozone — as found in the 

 air. It has been sup]:)0Sed to be a form or derivative from 

 oxygen. It is an active oxidizing agent, and a purifier of the 

 atmosphere. It is found in larger cpiantities outside than 

 inside of cities. It exists in considerable proportion in ever- 

 green forests, and much good has been ascribed to it in the 

 "Wood's life" of the consumptive. There is, however, much 

 difference of opinion as to its true constitution and import, 

 and it has not been availal)le practicall}'. 



LIC.HT. 



Of light, in its relations to health, we can say naught, except 

 of its beneficences. It has not such direct vital relations with 

 the human system as the atmosphere ; it is not .so demon- 

 strably necessary as it is — yet there is no doubt of its import- 

 ance in the molecular changes going on at the surface of the 

 l)ody. Mrs. Browning has given a poetical expression of this, 

 when she speaks of "taking the winds into our pulses and 

 mixing sunshine with our blood." Light is more pervasi\-e 

 in its distri])ution than oxygen, l)ut necessarily, on account 

 of the alteration of night and day, is not continuous in 

 action. Its necessity in ]->romoting vegetable growth is 

 common knowledge. vSuch a reversal as takes i)lace in 

 the atmospliere during the night in regard to the (|uantil>- 

 of carbonic acid and oxygen is sufficient evidence of the 

 importance of light to the vegetable world. This is produced 



