PURE AND IMPURE FOODS. 



" What a Man Eats He Is." 



Edited by C. F. Langworthy, Ph.D. 



Author of " On Citraconic, Itaconic and Mesaconic Acids," " Fish as Food,'' etc. 



THE RESPIRATION CALORIMETER. 



An instrument which has proved of great 

 value for studying the fundamental laws of 

 nutrition, as well as more practical prob- 

 lems, is the respiration calorimeter, so 

 called because it is used to study the 

 products of respiration, and to measure 

 energy in the form of heat. In experiments 

 with the instrument, all the income of tne 

 body (food, drink, and inspired air) and all 

 the outgo are measured, as well as the fuel 

 value of the food (the incot e of energy) 

 and the outgo of energy (the muscular 

 work performed and the heat given off by 

 the 1 ody). 



The respiration calorimeter was devised 

 by Professors W. O. Atwater and E. B. 

 Rosa, i ider the auspices of the United 

 States Departme t of Agriculture and 

 Wesleyan University. It consists of a 

 copper box surrounded by one zinc and 3 

 wo wa!ls, separated by air spac^,. The 



calorimeter stands in a large room which 

 also contains the pump for forcing a cur- 

 rent of air through it, and many other in- 

 struments and appliances for making neces- 

 sary measurements. The cop- r box is 

 really a small room about 7 feet long, 4 

 feet wi and 6 T /> feet hig. . It s fur- 

 nished with a folding bed, folding table, 

 chair, etc., so that a man may remain in it 

 in comparative comfort several days or 

 even weeks. There is a window in front 

 through which the man experimented on 

 enters the chamber. This closes air-tight. 

 Sufficient light for reading, etc., is ad- 

 mitted through this window. A telephone 

 enables the man in the chamber to com- 

 municate with those outside. All the air 

 which is required enters the chamber 

 through a pipe in the front of the appa- 

 ratus and leaves it through another pipe. 

 The current is maintained by a pump 

 which is an ingenious device. It not only 

 draws the necessary quantity of air through 

 the chamber, but it measures the quantity 

 automatically and delivers a sample for 

 analysis. The air current can be regulated 

 at will, and is always large enough to 

 secure comfort and prevent overheating the 

 chamber and the accumulation of moisture. 

 All the food and drink required are passed 

 through a tube in the side wall of the ap- 

 paratus. This has a cap on each end. One 

 cap is removed, the food or other article is 



placed in the tube, and the cap is again 

 screwed on. The man in the chamber then 

 unscrews the cap on the inside and removes 

 the food. The 2 caps are never removed at 

 the same time, and thus no appreciable 

 quantity of air can enter the chamber in 

 this way. The excreta are collected in 

 suitable vessels and passed out through the 

 same tube. All the food and excreta are 

 weighed and samples are analyzed. The in- 

 coming and outgoing air is also measured 

 and analyzed. The outgoing air differs 

 from that entering the chamber, since it 

 contains the carbon dioxide and water va- 

 por given off from the lungs. These result 

 from the burning up or oxidation of food 

 in' the body just as they result from the 

 consumption of fuel in a furnace. The body 

 is often likened to an engine and food to 

 fuel. The body differs from an engine in 

 that it is in itself built up from the elements 

 contained in its fuel, and any excess over 

 the amount required for building and re- 

 pairing tissue and for the work performed 

 may be stored as reserve material, chiefly 

 fat. 



The respiration calorimeter is so ar- 

 ranged that no heat can pass through the 

 walls from the outside or vice versa. All 

 the heat given off from the man's body 

 inside the chamber serves to warm a cur- 

 rent of cold water which circulates in a 

 pipe passing around tne inside 01 the cham- 

 ber. This device suggests the system com- 

 monly employed of heating houses by means 

 of hot water. The hot water brings heat 

 into the room where it is given off, the 

 partially cold water returning to the boiler. 



In the respiration calorimeter the cold 

 water enters the chamber, is warmed, and, 

 flowing out, carries the heat with it. By 

 measuring the volume of water which 

 passes through the pipe and its tempera- 

 ture on entering and leaving the chamber, 

 the amount of heat can be easily calculated. 

 The latent heat contained in the food and 

 represented by its fuel value is liberated 

 when food is burned in the body. This heat 

 serves for maintaining the body tempera- 

 ture, supplies the energy necessary for the 

 circulation of the blood, the beating of the 

 heart, and for all work performed. The 

 resultant of all forms of work is heat; 

 that is, the energy which is used to per- 

 form work is converted into heat. This is 





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