494 



SCIENCE. 



[N. S. Vol. V. No. 117. 



terials are taken into the body and what 

 are removed from it. Arrangements are 

 also made for regulating the temperature 

 inside the chamber. In these experiments 

 cold water is passed through tubes in the 

 respiration chamber. These tubes act as 

 absorbers, the heat given off from the body 

 being taken up and carried away by the 

 current of cold water. In this manner the 

 temperature is kept at a point which is 

 comfortable for the occupant at all times. 

 This is the reverse of the system followed 

 in heating houses by means of hot water 

 passed through radiators from which the 

 heat is given off into the rooms. A man 

 can remain in the respiration chamber an 

 indefinite time without particular incon- 

 venience. The experiments thus far made 

 have been of from 2i to 12 days' duration. 

 The assistant who remained in the cham- 

 ber during the longest experiment expe- 

 rienced so little inconvenience that he is 

 by no means unwilling to undertake the 

 same task during a period of even longer 

 duration. Observers are at hand day and 

 night. They not only attend to the wants 

 of the subject and supply him with food 

 and drink, but also make the weighings, 

 measurements and analyses needed for the 

 experiment. 



THE EXPERIMENTS AND THEIE RESULTS. 



These can be best explained by first de- 

 scribing the diet and its nutritive ingredi- 

 ents and then referring to the effects of the 

 food upon the body of the subject. Facts 

 drawn from several of the experiments will 

 be used for this purpose. The first experi- 

 ment was made with a laboratory janitor. 

 He was a Swede about thirty j'ears old and 

 weighed, without clothing, 148 pounds. 

 He was accustomed to rather active muscu- 

 lar labor, and previous experiments had 

 shown him to be a decidedly ' hearty ' 

 eater. He remained two and one-fourth 

 days in the apparatus. He drank water 



ad libitum. His daily food was as follows ' 



Ounces. 



Cooked meat 4.3 



Eggs 3.5 



Potatoes 5.3 



Bread 8.8 



Milk crackers 3.5 



Butter 1.1 



Cheese 2.7 



Milk 35.1 



Sugar 0.8 



Coffee 10.5 



Total 75.6 



During the experiment the subject didno' 

 work ; he read a little, but had extremely 

 little muscular exercise. The diet was- 

 necessarily simple because of the labor re- 

 quired for the preparation, measurement 

 and analysis of the foods. It was, how- 

 ever, entirely agreeable to the subject and 

 the quantities were such as he chose. Im 

 estimating the quantities of nutritive in- 

 gredients of the food it is customary to take 

 into account the protein, fats and carbohy- 

 drates and the potential energy or fuel 

 value. The protein compounds which oc- 

 cur, for example, in the lean of meat, white 

 of egg, casein of milk, gluten of wheat, 

 are the so-called tissue-forming substances. 

 They make blood and muscle, bone and 

 brain. The fats include the fat of meat^ 

 the fat of butter and milk, the oil of wheat^ 

 etc. The carbohydrates are the sugars and 

 starches, such as the starch of bread and 

 potatoes and ordinary sugar. The fuel 

 values are estimated in heat units or ca- 

 lories. The fats and carbohydrates are 

 the chief fuel ingredients of the body, 

 although the protein compounds serve to 

 some extent as fuel. But while the pro- 

 tein compounds can do the work of the 

 fats and carbohydrates in supplying fuel 

 for warmth for the body and for its- 

 muscular work, neither fats nor carbohy- 

 drates can take the place of the protein in 

 building and repairing the tissues of the 

 body. In considering the nutritive in- 



