The Nutrition Laboratory has already carried out an extensive research with one of the ingenious gas-analysis apparatus of Sonden.5 This apparatus, which is designed primarily for studying the composition of outdoor air, permits the determination of carbon dioxide to three significant figures, that is, to 0.001 per cent. An accuracy of 0.001 per cent is possible in determining oxygen. The particular form of Sonden-Pettereson apparatus used by Sonden and Tigerstedt was designed especially for the determination of carbon dioxide only and an even greater degree of accuracy was possible. Indeed, with their apparatus it was possible to determine the carbon dioxide with an accuracy of 0.0001 per cent. This extraordinary accuracy made it possible for the Stockholm investigators to utilize their large respiration chamber for studying the metabolism of a single individual in complete muscular repose. It is obvious, however, that an apparatus of this type requires an especially capable gas analyst.

1 Since this was written, such a research has been begun by the Nutrition Laboratory, at the Agricultural Experiment-Station, Durham, New Hampshire. 2 Sonden and Tigerstedt, Skand. Arch. f. Physiol., 1895, 6, p. 1. 3 Tigerstedt, Skand. Arch. f. Physiol., 1906, 18, p. 298. 4 Pettersson, Zeitschr. f. anal. Chem., 1886, 26, pp. 467 and 469; Pettersson and Palmquist, Ber. d. deutsch. chem. Gesellsch., 1887, 20, p. 2129; Sonden, Zeitschr. f. Instrumentenkunde, 1889, 9, p. 472. 5 Benedict, Carnegie Inst. Wash. Pub. No. 166, 1912.

The dimensions of the Stockholm and Helsingfors chambers seemed to us much too large for ordinary observations on groups of individuals or with severe muscular work. It was therefore considered that in building the group chamber for the Nutrition Laboratory it would be advantageous to minimize the volume in so far as would be consistent with flexibility in adapting it to the types of experiment desired. Accordingly, a chamber with approximately one-half the volume of the Helsingfors chamber was constructed.

The first research in which the group respiration apparatus was employed was one which has been in progress for a year or more in cooperation with Simmons College, namely, the study with a group of young women of college age of both the resting requirements and the carbon-dioxide production during various domestic activities. The original intention was to describe this apparatus in detail in the published report of the research with the Simmons College students. The exigencies of the situation, however, demand that a somewhat lengthy description should be given here of the technical apparatus used for a considerable number of observations in this research on undernutrition.

The entire apparatus has been built by the construction staff of the Nutrition Laboratory. To Mr. W. E. Collins and his assistant, Mr. F. A. Renshaw, our appreciation is here expressed for the skilful way in which the apparatus was constructed.