236 PRINCIPLES OF ANIMAL NUTRITION. 
sists in burning the suhstance without any admixture in highly 
compressed oxygen contained in a lined steel bomb as first devised 
by Berthelot * and subsequently modified by Mahler, Hempel, and 
Atwater. With this type of calorimeter very accurate and com- 
paratively rapid work may be done.t , 
Frankland was the first to undertake determinations of the 
heats of combustion of foods and food ingredients, using the origi- 
nal form of the Thompson calorimeter. Subsequent investigators, 
of whom may be especially mentioned Stohmann, v. Rechenberg 
and Danilewski, Berthelot and his associates, Rubner, and Atwater, 
Gibson & Woods, have continued these investigations with im- 
proved apparatus and more refined methods,{ and we now possess 
a considerable mass of data as to the heats of combustion of the 
more important ingredients of animals and plants and of the prod- 
ucts of metabolism. Atwater § gives the following summary of 
the results on record up to July, 1894 (see pp. 237-9). 
In the course of recent investigations into the energy relations 
of the food of man and of domestic animals a considerable amount 
of data has also been secured regarding the heats of combus- 
tion of foods and feeding-stuffs. A summary of the results of 
such determinations on 276 samples of human foods of various 
kinds has been published by Atwater & Bryant. No similar 
compilation of heats of combustion of feeding-stuffs is as yet avail- 
able. 
It need hardly be pointed out that, taken by themselves, 
such results furnish no measure of the relative values of the 
various feeding-stuffs. Like a chemical analysis, they supply 
but a single factor, albeit an important one, for such a com- 
* Ann. de Chim. et de Phys., (5), 23, 160. 
t For the technical details of the method reference may be had to the 
published descriptions of the apparatus or to Wiley’s Principles and Prac- 
tice of Agricultural Chemical Analysis, Vol. III, p. 569. 
t For a historical sketch of the development of calorimetry, as afMlied 
to food substances, compare Atwater, “Chemistry and Economy of Food,” 
U.S. Department of Agriculture, Office of Experiment Stations, Bull. 21, pp 
116-126. 
§ Ibid., pp. 127 and 128. Compare also Rep. Storrs Expt. Station, 1899, 
p. 73. 
|| Rep. Conn. Storrs Expt. Station, 1899, p. 97. 
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