APPARATUS AND METHODS USED IN THIS RESEARCH. 33 



had to do with the metabolism of men, there was very little demand for 

 a small respiration apparatus. There are, however, many physiological 

 laboratories and laboratories in hygienic institutes and medical clinics 

 that wish to utilize an apparatus, not only for experiments with men 

 but also with animals. Such a possibility has already been demon- 

 strated, notably by Grafe 1 in Heidelberg and by Roily 2 in Leipsic. A 

 small apparatus, which is based upon the principle of the large respira- 

 tion calorimeters used in this laboratory, has been here devised for 

 experiments with men; this has already been described in detail. 3 

 While the fundamental principle has not been altered in any way, the 

 apparatus has from time to time been modified and improved, and a 

 cage or respiration chamber added, thus making observations possible 

 with small animals and with infants. Its use with animals was first 

 described by Benedict and Homans; 4 it was later referred to in a 

 paper by Benedict and Talbot 5 as being used for observations with 

 infants. In these earlier descriptions, it was stated that the apparatus 

 had been only so far perfected as to permit the measurement of the 

 carbon-dioxide excretion and did not permit the measurement of the 

 oxygen consumption. Since these publications have appeared, a newer 

 type of this apparatus has been devised and at least two investigations 8 

 have been reported from this laboratory in which the apparatus was 

 used. The large number of respiration apparatus devised in the Ameri- 

 can and foreign laboratories make it practically impossible to contribute 

 any fundamentally new features to the study of animal metabolism 

 along this line. Nevertheless, as the main object in devising the appa- 

 ratus used in this laboratory was to make it so flexible that it could be 

 employed not only for men but likewise for infants and for large and 

 small animals, a description of this later form seems desirable before 

 further investigations are reported. 



While the new feature in this modified apparatus is the direct deter- 

 mination of the oxygen consumption, opportunity is again taken here 

 to emphasize strongly the importance of graphic records of the muscular 

 activity in experiments with all classes of subjects, including not only 

 men but infants and small animals, and also to emphasize the import- 

 ance of the pulse-rate as an index of the intensity of the metabolism. 

 Every respiration experiment conducted in this laboratory consists 

 always of two parts, each indispensable to the other and each valueless 

 without the other; first, the chemical division, i. e., the measurements 

 of the carbon-dioxide excretion and the oxygen consumption; and, 



J Grafe and Graham, Zeitschr. f. physiol. Chem., 1911, 73, p. 7. 



2 Rolly and Rosiewicz, Deutsch. Archiv f. klin. Med., 1911, 103, p. 58. See also discussion 

 of Rolly's apparatus by Grafe, Abderhalden's Handbuch der biochemischen Arbeitsmethoden, 

 1913, 7, p. 524. 



Benedict, Deutsch. Archiv f. klin. Med., 1912, 107, p. 156. 



4 Benedict and Homans, Journ. Med. Research, 1912, 25, p. 409. 



"Benedict and Talbot, Am. Journ. of Diseases of Children, 1912, 4, p. 129. 



6 Benedict and Pratt, Journ. Biol. Chem., 1913, 15, p. 1; Morgulis and Pratt, Am. Journ. 

 Physiol., 1913, 32, p. 200. At this point it is a pleasure to acknowledge the helpful assistance of 

 Dr. S. Morgulis in developing the technique of determining oxygen with the apparatus. 



