July 16, 1915] 



SCIENCE 



77 



plying this weight by the temperature 

 difference. 



The chair calorimeter is of a different 

 shape, although primarily of the same con- 

 struction. In the chair calorimeter, the 

 subject sits in a comfortable arm chair, the 

 walls of the chamber being of such a form 

 as to give a minimum amount of air space 

 about the body. The total volume of air 

 space in the bed calorimeter is 950 liters, 

 and in the chair calorimeter 1,500 liters. 

 Neither apparatus, however, permits long 

 experiments. 



A third calorimeter has been built which 

 is long enough for a man to lie down in, 

 and yet high enough for him to stand up; 

 the form of the chamber aLso permits the 

 installation of a bicycle ergometer inside 

 the chamber for muscular work experi- 

 ments. The volume of air space in this 

 apparatus has been limited to 3,500 liters. 

 By means of a double port-hole it is pos- 

 sible to put in or take out food or other 

 material without loss of air. The subject 

 can live in this apparatus as long, if not 

 longer, than in the chamber at Wesleyan 

 University, Middletown, Conn., the longest 

 experiment with that apparatus covering 

 13 days and 14 nights. Thus far no con- 

 tinuous calorimeter experiments of any 

 considerable length have been made in the 

 Nutrition Laboratory. 



Finally, to provide a calorimeter espe- 

 cially designed for severe muscular work 

 with a bicycle ergometer, treadmill, or end- 

 less ladder, a calorimeter has been built 

 with provision for installing any one of 

 these muscular work appliances. Owing to 

 the great amount of heat that will be devel- 

 oped in such experiments, special heat-ab- 

 sorbing pipes and temperature measuring 

 apparatus have been necessary. 



With the respiration calorimeter it is pos- 

 sible to measure simultaneously the carbon 

 dioxide and water vapor produced, the 



oxygen consumed, and the heat given off by 

 a man. These factors taken not only indi- 

 vidually, but also together, give most impor- 

 tant data for the computation of the char- 

 acter and amount of the interchange of 

 material inside of the body due to vital 

 processes. 



Fortunately it was found that the long 

 and costly twenty-four-hour calorimeter ex- 

 periments could be in part replaced by 

 shorter experiments, in which only the 

 carbon-dioxide production and oxygen con- 

 sumption were studied, by means of a 

 respiration apparatus devoid of ealorimetrie 

 features and that this type of short experi- 

 ment could be used in the study of many 

 problems. An apparatus was devised by 

 which a subject lying on a bed could 

 breathe through a mouth- or nosepiece, and 

 determinations of the carbon dioxide pro- 

 duced and the oxygen consumed could be 

 made in periods as short as 15 minutes. 

 These experiments have been carried out 

 very rapidly and at relatively slight ex- 

 pense, and have been of great value in 

 giving us a large amount of important 

 physiological information. In recent years, 

 the calorimeters have also been used for 

 short experiments, these being from one to 

 two hours long; indeed, the research on 

 diabetes, which has been in progress in the 

 Nutrition Laboratory for the past six years, 

 has relied for the most part on calorimeter 

 experiments of from one and one half to 

 two hours' duration. 



The influence of muscular activity upon 

 the production of carbon dioxide and heat 

 is enormous. When a subject is sound 

 asleep, quiet and without food in the 

 stomach, we have the minimum basal 

 metabolism. The influence of sleep has 

 only been tardily recognized, and the major- 

 ity of physiologists are inclined to speak of 

 basal metabolism as that obtained in the 

 early forenoon, when the subject is lying 



