NUTRITION LABORATORY. 261 



to the cooling effect upon the skin of the vaporization of water and to the 

 comparison of the skin temperature with that taken deep in the body. 



Influence of environmental temperature upon metabolism. — With the clothed 

 human individual the temperature environment of the skin is usually fairly 

 constant, although it is by no means uniform in all parts of the body. The 

 influence of altering environmental temperature by exposure of the nude body 

 to air at different temperatures, and particularly the cooling effect of moving 

 air, has been studied in its relation to the basal metabolism. The subject used 

 was the artist's model employed in former years. The details of the measure- 

 ments were chiefly in the hands of Miss Hendry and Miss Baker. 



Metabolism during mental effort. — This complicated problem has been inter- 

 mittently studied, with special attention to the influence of mental effort upon 

 respiratory rhythm and rate as well as the metabolism. Refinement of tech- 

 nique and methods is progressing, and the problem bids fair ultimately to be 

 attacked with most satisfactory methods. 



The insensible perspiration of humans. — The continuous, though slight, loss 

 in weight of the body has been designated as the "insensible perspiration," 

 this being made up in large part of the loss of water by vaporization from the 

 lungs and skin. With the nude subject employed in other investigations, a 

 series of measurements of the insensible perspiration under various conditions 

 of clothing, environmental temperature, and wind velocity have been made by 

 having the subject lie upon a non-hygroscopic bed, suspended on a large 

 balance having a sensitivity with full load of approximately 1 decigram. 

 Simultaneous measurements of the gaseous metabolism and of the trunk and 

 skin temperatures accompanied all of these measurements. The studies were 

 made with the cooperation of Miss Hendry. 



The emission calorimeter for humans. — It is believed that in many problems 

 a rapidly changing rate of heat emission from the human body can be measured 

 only by means of a calorimeter of design fundamentally different from any 

 thus far existing. Since at the moment of disrobing there is a profound dis- 

 turbance of heat-loss, special attention has been devoted to the construction of 

 an emission calorimeter large enough for humans. The development of this 

 apparatus has progressed with the assistance of Miss Baker. 



Metabolism of steers during fasting. — From the standpoint of comparative 

 physiology, a knowledge of the metabolism of steers during complete with- 

 drawal of food was necessary, and, indeed, the interpretation of the food needs 

 of these large ruminants can be properly made only by some suitable standard 

 of reference. During the past year two full-grown steers have been subjected 

 to several periods of complete fasting, ranging from 5 days to 14 days. During 

 this time the carbon-dioxide production has been carefully measured and 

 unusual care has been given to the collection and analysis of the excreta. 

 The details of the investigation have been in the hands of Professor E. G. 

 Ritzman, at the New Hampshire Agricultural Experiment Station in Durham, 

 New Hampshire, where the apparatus is installed. Professor Ritzman has 

 been assisted by Miss Helen L. Hilton. The addition of special gas-analysis 

 technique has been possible through the assistance rendered by Dr. Carpenter 

 and Miss Baker, of this Laboratory. 



The gaseous metabolism of the white rat. — With the rat colony at Columbia 

 University, in the department of Dr. H. C. Sherman, a cooperative research 



