nutrition laboratory. 1 85 



e;xpe;rime;nts on the influence of the preceding diet upon the 



respiratory exchange. 



The relation between the amount of carbon dioxide excreted in the breath 

 and the amount of oxygen absorbed gives an interesting and relatively accu- 

 rate picture of the nature of the material burned in the body. Under ordi- 

 nary conditions of diet, it is commonly assumed that 12 hours after the last 

 meal the body is living substantially upon the same kind of material. This 

 value has been designated by German investigators as the "nuchternwert" and 

 is but inadequately expressed by the term "fasting value." It certainly does 

 not represent the interchange of material after prolonged fasting. Indeed, 

 after 48 hours, this value may be very materially changed. 



In order to throw some light upon the fluctuations of this value as affected 

 by the preceding diet, a series of experiments has been begun with the new 

 respiration apparatus mentioned above, and a large amount of material has 

 already been accumulated. The research will show that the ingestion of large 

 amounts of carbohydrate, even though it be 12 hours before the experiments 

 are made, materially influences the respiratory ratio. The experiments are 

 still in progress, the technique has been perfected, and the results prove to 

 be of considerable interest. The experiments are being carried out by Messrs. 

 J. A. Riche and L. E. Emmes, of the laboratory staff. 



COMPOSITION OF OUTDOOR AIR. 



Innumerable analyses of outdoor air have been made by different investi- 

 gators with particular reference to the carbon-dioxide and oxygen content. 

 The variations found are very considerable. A careful inspection of the 

 results shows that the variations may be due to the proximity to a large 

 city, the direction of the wind, the moisture content of the air, and, above all, 

 to the methods of analysis. As a result of a conference that I had with Mr. 

 Sonden in Stockholm two years ago, he devised and Grave constructed for 

 us a most intricate apparatus for the analysis of atmospheric air. During 

 the past winter Miss Alice Johnson, of this staff, has been making a large 

 number of analyses of outdoor air taken from either side of the laboratory 

 building. The results show the extraordinary accuracy of the apparatus, the 

 remarkable constancy in the amount of carbon-dioxide in the outdoor air, 

 and the occasionally noticeable fall in the oxygen content, the cause of which 

 has not as yet become perfectly clear. 



ANALYSES OF FOOD, FECES, AND URINE OF THE ESKIMOS. 



In consultation with Dr. August Krogh, of the University of Copenhagen, 

 during my trip to Europe in 1907, a cooperative investigation into the com- 

 position of the foods, feces, and urine of Eskimos was tentatively planned. 

 During the summer of 1908 Dr. and Mrs. Krogh went to the Danish Arctic 

 station in Greenland and there established a portable respiration apparatus 



