22 ON THE INFLUENCE 



bell-glass. This was repeated two or three times, 

 and the air in the bottle was then preserved for 

 examination. The proportion of carbonic acid 

 having been ascertained, and the capacities of 

 the different parts of the apparatus, and the 

 space occupied by the animal being known, the 

 total quantity of carbonic acid formed, and con- 

 sequently of oxygen consumed, was easily esti- 

 mated. 



When the experiment was made on an animal 

 in whom the functions of the brain were de- 

 stroyed, and in whom therefore voluntary respi- 

 ration had ceased, the narrow extremity of the 

 tube was inserted into an artificial opening in 

 the trachea, and the animal being placed under 

 the bell-glass, the lungs were inflated at regular 

 intervals, by means of pressure made on the gum- 

 bottle. The tube being smaller than the trachea, 

 the greater portion of the air in expiration escaped 

 by the side of the tube into the general cavity of 

 the bell-glass, while the gum-bottle filled itself 

 by its own elasticity with air through the open- 

 ing G. At the end of the experiment, a portion 

 of air was preserved for examination, and the 

 quantity of carbonic acid was estimated in the 

 way already described. 



The animals employed in these experiments 

 were of the same species, and nearly of the same 

 size. Attention to these circumstances was 

 judged necessary, that the results might be as 

 little liable to error as possible. The chemical 

 examination of the air, was made by agitating it 



