408 On the Influence of the Brain 



the fiinclions of the hrain were destroyed, and in whom 

 therefore voluniary respiration had ceased, ihe narrow ex- 

 tremity of the tube was inserted into an artificial opening 

 in the trachea, and the anniial heing placed under the bell- 

 glass, the lungs were inflated at regular intervals, by means 

 of pressure n)ade 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 opening G. At 

 the end of the experiment, a portion of air was preserved 

 for examination, and the quantity of carbonic acid was esti- 

 mated 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 re- 

 sults might be as conclusive as possible. The chemical 

 examination of the air was made by agitating it in a gra- 

 duated measure over quicksilver, with a watery solution of 

 potash. My friend Mr. Brande gave nie his assistance in 

 this part of the present investigation, as he had done on 

 many former occasions. It will be observed, that in esti- 

 mating the proportion of carbonic acid, no allowance has 

 been made for that contained in the atmospheric air; first, 

 because the quantity is so small that the on)ission can oc- 

 casion no material error; and secondly, because the object 

 is to ascertain, not so much the absolute as the relative 

 quantities of carbonic acid evolved by animals breathing 

 inider different circumstances. 



The experiments which I shall first notice, were made 

 on the respiration of animals in a natural slate. 



Experiment I. — Thermomeler Gb^, barometer not noted. 



A young rabbit was allowed to remain under the bell- 

 glass during 30 minutes. The respired air at the end of 

 this time was found to contain -^-^ of carbonic acid. 



k was ascertained that the rabbit occupied the space of 

 50 cubic inches. 



The capacity of the bell-glass = 502 cubic inches. 



That of the gum-bottle 52 cubic inches. 



The air in the tubes and bladder = 2 cubic inches. 



„, 50'.>. + 52 + '2 - 50 .50(5 



Then = ^^ = 25-3. 



The rabbit therefore in 30 minutes gave out 25-3 cubic 

 inches of carbonic acid, and consumed the same quantity of 

 oxvgen gas, which is at the rate of 60"C in an hour. 

 Experiment 2. — Thermometer C5°, barometer 30 1 inch, 



A some- 



