OF THE BRAIN, ETC. 21 



connected with each other and with the rest of 

 the apparatus, and the circular groove is filled 

 with quicksilver. 



The capacity of the bell-glass, allowance being 

 made for the rim, which is received in the groove 

 with the quicksilver, is found to be 502 cubic 

 inches. The capacity of the gum-bottle is 52 

 cubic inches, and in the calculations after the 

 experiments, two cubic inches have been allowed 

 for the air contained in the different tubes, and 

 for the small remains of air in the bladder after 

 being nearly emptied by pressure. 



Mode of using the Apparatus. 



In order to ascertain the quantity of air con- 

 sumed under ordinary circumstances, the animal 

 was placed on the stand under the bell-glass, the 

 bladder having been emptied by pressure, and 

 the gum- bottle distended with atmospheric air. 

 During the experiment, by pressing occasionally 

 on the gum-bottle, the air was forced from it 

 into the bell-glass. On removing the pressure, 

 the gum-bottle became filled by its own elas- 

 ticity with air from the bell-glass. Thus the 

 air was kept in a state of agitation, while the 

 dilatation of the bladder prevented it from being 

 forced through the quicksilver under the edge of 

 the bell-glass. At the end of the experiment, the 

 gum-bottle was completely emptied by pressure, 

 and allowed to be again filled with air from the 



c 3 



