592 EXPERIMENT STATION RECORD. 



the required iiinouiit of eiierjLjy iu the form of or<;aMic matter is not 

 forthcoming. LTiuler the same conditions an animal starves also. 



If by artificial means the chlorophyll apparatus is hindered from its 

 normal functions the sprouting plant lives only until reserve material 

 in the seed is exhausted. Plants with green leaves increase iu weight 

 and store up reserve material in their tissues and organs, and build new 

 tissue and new organs when tlie conditions are such that they can pro- 

 duce more organic substance than is necessary for bare existence. 

 When an animal obtains more organic substance than is necessary for 

 carrying on its lite processes, be this the production of heat or muscular 

 energy, the excess is stored up iu the organism iu the form of fat, just 

 as in plants, under like conditions, starch, sugar, and fat are stored up. 

 Although normal gi'owtli in a plant or animal is completed by the aid 

 of organic substances, the inorganic compounds are also necessary. 

 Without certain salts it is impossible for a plant to produce organic 

 substances or for an animal to maintain life. This fact is self evident 

 and is only mentioned to avoid the possibility of misunderstanding. 



Organic substances furnish the animal almost entirely, and the plant 

 in large measure, with the energy necessary to sustain life processes. 



The determination of the heat equivalent of these substances must 

 be of the greatest importance in the study of the laws of nutrition, 

 since it furnishes a means of measuring the i^otential energy in these 

 compounds. 



I have devoted much time to the study of this problem since 1877. 

 At that time only one publication on the subject had appeared. This 

 was by Frankland,^ in 1860. He followed a method of investigation 

 devised by Lewis Thompson. Tliis consisted in mixing the organic 

 substance in the proper i^roportion with potassium chlorate and burn- 

 ing it in a (;alorimeter in such a manner that the gases of combustion 

 passed through water and there gave up their heat. The method 

 seemed extremely simple, and the apparatus was so easily made that 

 apparently it was only necessary to follow in Frankland's footsteps to 

 obtain satisfactory results. 



On close examination, however, it became apparent that neither the 

 method nor the apparatus as Frankland used it sufficed for accurate 

 results. It was also evident that it was only necessary to eliminate 

 ceilain errors from the method to make it available for exact research. 



I described an improved method in 1879.^ But even in this form the 

 method and apparatus were not sufiicient for such results as I desired 

 to obtain. Many improvements were made and many earlier results 

 were thrown aside until at last, in 1884,^ the method was ])erfected. In 

 elaborating the method the difficulties to be overcome arose from the 



1 Phil. Mag., 4th ser., 32, p. 182. 

 * Jour. prak. Chem., 19, p. 115. 

 'Laudw. Jahrb., 13 (1884), p. 513. 



