RATE OF OXYGEN CONSUMPTION 



183 



one inch), and then to the gradual consumption of this 

 oxygen by the dog during which interval the disc will be 

 falling (one inch). During all this time the exhaled car- 

 bon dioxide is being absorbed by the alkali solution. The 

 twine string attached to the disc passes over two pulleys 

 (one inch brass wheels these should be of the best quality 

 and can be bought at any good hardware store for about 

 twenty or thirty cents apiece). The opposite end of the 



Fig. 175. A simpler arrangement for recording the rate and amount of oxygen 

 consumption by an animal. (See also Fig. 172.) There is more chance for "lost mo- 

 tion" by use of the flexible bath cap over the pan than with the apparatus shown in 

 Fig. 172. (See Journal of Laboratory and Clinical Medicine, 1916, ii, p. 94.) 



string is clamped on to the long arm of a frog heart lever 

 by means of a bull-dog clamp. Two clamps may be neede'd 

 to draw the lever down readily. These clamps serve not 

 only to hold the string to the lever but act as balancing 

 weights as well. The heart lever writes at the top of 

 the drum, below this is the blood-pressure (mercury ma- 

 nometer), next the respiration (tambour connected to the 



