NUTRITION LABORATORY* 



Francis G. Benedict, Director. 



The past year has witnessed an unusually active interest in the laboratory 

 on the part of cooperating and visiting investigators. The construction of 

 new apparatus and the improvement of apparatus already in use have added 

 materially to our equipment, while the experimental researches have led to 

 the accumulation of a large amount of important data with regard to a 

 number of questions of fundamental importance in both physiology and 

 pathology. 



ADDITIONS TO EQUIPMENT. 



The wisdom of constructing one large room without obstructing columns 

 or piers and provided with arrangements for cooling and drying the air for 

 use in calorimetric research has been fully justified in the past three years of 

 experimenting ; indeed, during the warmer months, the tendency has been to 

 move to this room all researches in the building that can possibly be trans- 

 ported, and thus utilize the equable temperature and admirable humidity 

 conditions. To facilitate this as much as possible, the available floor-space 

 in the room has been increased materially during the last year by the addition 

 of another balcony, somewhat larger than the one constructed a year ago. 

 By this means it will be possible in future to conduct a larger number of 

 researches in the calorimeter room during the warm weather; additional 

 desk-room is also provided for one or more associates during the winter, 

 thus permitting a more direct personal supervision of the researches in the 

 calorimeter room than can otherwise be had. 



ALTERATIONS IN THK RESPIRATION CALORIMETERS, 



In an effort to minimize all possible sources of error in the calorimetric 

 researches, it was found that the structural-steel framework of the respira- 

 tion calorimeters has a capacity for holding or absorbing heat, thus affecting 

 to a certain extent the heat measurements. In some of the calorimeters this 

 interior framework was directly connected with the outer air through bolts 

 or pieces of structural steel. It was assumed that the slight temperature 

 differences between the inside of the chamber and the room air, namely, 2° 

 or 3°, would not result in a material conduction of heat; but with the greater 

 accuracy now striven for, it was deemed desirable this past winter to com- 

 pletely isolate the structural-steel framework by using rock-maple supports, 

 and thus insure a perfect insulation from the room air. This insulation has 

 been carried out on three of the calorimeters with the highest degree of 

 success. 



* Situated at Boston, Massachusetts. Grant No. 681. $30,378 for investigations and 

 maintenance during 191 1. (For previous reports on work in nutrition, see Year Books 

 Nos. 2-9.) 



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