SUGGESTIONS FOR LABORATORY WORK 627 



METABOLISM 



The Influence of Muscular Exercise on Carbon Dioxide Produc- 

 tion. Make the first observation described below after at least 

 one hour of relative inactivity. 



Fill a large wide-mouthed bottle with water and invert over a 

 reservoir of water. Insert a good sized rubber or bent glass tube 

 into the neck of the bottle. Place the other end in the mouth. 

 Hold the nose during each expiration and blow all the expired air 

 into the bottle. Note carefully the number of expirations and the 

 time required for filling the bottle with expired air. Cork the 

 bottle tightly and turn right side up. 



Fill a narrow test tube with strong sodium hydroxide solution. 

 Cork. Tie a thread about the test tube and by means of this 

 thread lower the tube carefully into the bottle of expired air. 

 Restopper this bottle tightly and then by jarring it break the test 

 tube, liberating the alkali. Shake thoroughly. The alkali takes 

 up the carbon dioxide. Invert the bottle again over the reservoir 

 of water. With the neck under water remove the stopper. Water 

 rushes in to replace the absorbed carbon dioxide. Lower the 

 bottle till the water is at the same level inside and outside. With 

 the bottle in this position replace the stopper. The volume of 

 water enclosed equals that of the carbon dioxide in the entire 

 bottle of expired air. Determine this volume with the aid of a 

 graduated vessel. Calculate the volume of carbon dioxide 

 exhaled with each breath and also the volume exhaled per 

 minute. 



Rinse the bottle out thoroughly to remove all traces of sodium 

 hydroxide. Take several minutes of very brisk exercise. As 

 quickly as possible after the cessation of the exercise repeat the 

 experiment above. Care must be taken that all the air expired 

 during the period of collection enters the bottle. The augmented 

 breathing makes this a matter of some difficulty. There are numer- 

 ous sources of error in this experiment, but if carefully performed 

 it demonstrates a marked increase in the carbon dioxide produc- 

 tion per minute with exercise, and a suggestion as to the amount 

 produced. 



A Study of Urine. Urine is the chief excretion of the body. It 

 contains the greater portion of the end-products of protein metab- 



