on the Influence of the Brain , &c. 381 
a right angle with the rest of the tube, passes through a hole 
in the wooden stand, and projects into the cavity of the bell- 
glass, where it makes a second turn also at a right angle, and 
becomes of a smaller diameter. In the upright part of the 
tube is an opening G. 
The tubes are made perfectly air-tight, where 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 ex- 
periments 2 cubic inches have been allowed for the air con- 
tained 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 consumed under 
ordinary circumstances, the animal was placed on the stand 
under the bell-glass, the bladder being emptied by pressure, 
and the gum-bottle being 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 re- 
moving the pressure, the gum-bottle became filled by its own 
elasticity with air from the bell-glass. Thus the air was kept 
in a state of agitation, and the dilatation of the bladder pre- 
vented the air 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 bell-glass: this was repeated 
mdcccxii. 3 D 
