TECHNIQUE FOR METABOLISM DURING REST. 93 



intensity of metabolism has been accurately measured with the univer- 

 sal respiration apparatus, both by Cathcart^ and by Murschhauser.^ 

 The measurements are, however, confined to those for one person and 

 no attempt has been made to utilize the apparatus in connection with a 

 large respiration chamber. 



A larger apparatus, based on essentially the same principle as the 

 universal respiration apparatus, was used with a respiration chamber 

 in the chemical laboratory at Wesleyan University, Middletown, Con- 

 necticut, for studying the carbon-dioxide output during the severe 

 muscular work of bicycle riding. With the universal respiration 

 apparatus the periods must be limited to 10 or 15 minutes. With 

 the respiration chamber at Wesleyan University periods as long as 

 1 or 2 hours could be used. With this apparatus all of the carbon 

 dioxide produced was absorbed from the ventilating air current by 

 soda-lime, thus calling for literally enormous amounts of soda-lime. 

 As a matter of fact, three large soda-lime cans in series were required 

 to absorb the 200 or more grams of carbon dioxide produced in one 

 hour.^ Since these earlier experiments were for only a few hours, this 

 particular proceeding was neither too time-consuming nor too expen- 

 sive, but if a research were undertaken in which a large amount of 

 carbon dioxide was produced over a considerable period of time, the 

 question not only of the expense but of the mere matter of provid- 

 ing sufficient soda-lime would be a very serious one. 



With the universal respiration apparatus it would be easy to develop 

 two independent sets of absorbing systems and shift from one to the 

 other at the end of every 15 to 20 minutes, but even then the mechan- 

 ism would not permit the absorption at a maximum of more than 3,000 

 c.c. per minute. Consequently, for a research involving the simulta- 

 neous measurement of the carbon-dioxide production of a number of 

 individuals, such as in group experiments, this particular type of appa- 

 ratus would not suffice. 



The Nutrition Laboratory has long recognized the need of a large 

 chamber in which not only a group of individuals could be studied 

 simultaneously but two, three, or more individuals could be made 

 to perform intense muscular work and their carbon-dioxide produc- 

 tion during the activity accurately measured. Precisely this type of 

 problem presents itself to all workers in animal nutrition, for the carbon- 

 dioxide production with large domestic animals is so great as to demand 

 extremely costly and elaborate apparatus, such as the marvelous in- 

 stallation of Professor H. P. Armsby^ of State College, Pennsylvania. 

 While the Nutrition Laboratory is not engaged in research with large 



1 Benedict and Cathcart, Carnegie Inst. Wash. Pub. No. 187, 1913. 

 ^ Benedict and Murschhauser, Carnegie Inst. Wash. Pub. No. 231, 1915. 

 3 Benedict and Carpenter, U. S. Dept. Agr., Office Expt. Sta. Bui. 208, 1909, p. 31. 

 ■• Armsby and Fries, U. S. Dept. Agr., Bur. Animal Industry, Bui. 51, 1903; and Experiment 

 Station Record, 1903-1904, 15, p. 1037. 



