4:14 RESPIRATION. 



oxygen which is obtained by decomposing water by the Vol- 

 taic pile is in this condition. It exists in very small quantity 

 in the air, and plays no part in the function of respiration. 

 Its chief interest has been in a theoretical connection with 

 epidemic diseases. 1 Floating in the atmosphere are a num- 

 ber of excessively minute organic bodies. Various odor- 

 ous and other gaseous matter may be present as accidental 

 constituents. 



In considering the function of respiration, it is not neces- 

 sary to take account of any of the constituents of the atmos- 

 phere, except oxygen and nitrogen ; the others being either 

 inconstant, or existing in excessively minute quantity. It 

 is necessary to the regular performance of the function that 

 the air should contain about four parts of nitrogen to one of 

 oxygen, and have about the density which exists on the gen- 

 eral surface of the globe. When the density is very much 

 increased, as in mines, respiration is somewhat, though not 

 gravely, disturbed. By exposure to a rarefied atmosphere, as 

 in the ascent of high mountains or in aerial voyages, respira- 

 tion may be very seriously interfered with, from the fact that 

 less oxygen than usual is presented to the respiratory surface, 

 and the reduced atmospheric pressure diminishes the capa- 

 city of the blood for holding gases in solution. 



Magendie and Bernard, in experimenting on the minimum 

 proportion of oxygen in the air which is capable of sustaining 

 life, found that a rabbit, confined under a bell-glass witli an 

 arrangement for removing the carbonic acid and water ex- 



1 Ozone may be formed by passing electric discharges through the ordinary at- 

 mosphere, or through oxygen. Its proportion in the air is supposed to be much 

 increased in storms which are accompanied by electric phenomena. Schonbein 

 exposed animals to the action of this substance. A dog, confined for an hour in 

 a bell-glass, into which ozone was passed, died, though it was estimated that he 

 absorbed only about '03 of a grain. An examination showed the lungs in a con- 

 dition of acute inflammation. M. de la Rive, who has also experimented upon 

 it, compares its action on the respiratory organs to that of chlorine (BERNARD, 

 Le^ns sur les Effets des Substances Toxiques et Medicamentewes, Paris, 1857, p. 

 150). 



