CHEMICAL ENERGY 407 



the respiratory materials, such as sugar or oil, are able to be directly 

 oxidized owing to their fine subdivision and intimate association with proto- 

 plasmic molecules J . The fact that during the anaerobiosis of yeast and of 

 butyric bacteria sufficient energy is obtained by the intracellular fermenta- 

 tion of sugar produced by an enzyme capable of isolation 2 points to the 

 fact that sugar present in the cell can be decomposed without its being 

 chemically united with the protoplasm. 



The exact extent to which chemical, surface-tension, or osmotic energy 

 is used for the different forms of work carried out by the organism is 

 uncertain, but even if the chemical energy is not directly utilized, its trans- 

 formation still forms the essential accompaniment of all vital activity. 

 Similarly, the work done by all the machines in a factory is derived from 

 the chemical energy of the coal consumed, even when the energy of 

 expansion of the heated steam is used to drive an electric motor and the 

 electric energy transmitted to the different machines 3 . The special advan- 

 tage attached to the use of chemical energy in both manufactories and in 

 organisms is due to its forming a specially concentrated form of potential 

 energy which is readily rendered kinetic. 



The difference between the heat of partial or complete combustion of 

 the substance used in respiration and the actual production of heat indicates 

 how much of the realized chemical energy is converted into work, but says 

 nothing as to the details of the processes involved. Calorimetric investiga- 

 tions are nevertheless of great importance in the study of special questions, 

 although the utmost care is required even to obtain approximately accurate 

 results. In many cases, for instance, the quality and quantity of the 

 substances consumed and the degree of oxidation they undergo cannot be 

 exactly determined, so the amount of oxygen absorbed and of carbon 

 dioxide exhaled form unsafe guides as to the total heat of combustion 4 . 



Nor are we able to determine the heat equivalent of the mechanical 

 and other activities of the plant with sufficient accuracy. Owing to the 

 high mechanical equivalent of heat a considerable amount of work might 

 be done without the amount of heat liberated being appreciably lowered. 

 Furthermore, all energy used in overcoming friction or viscosity, or in 

 producing swelling, ultimately appears in the form of heat. Hence it 

 is not surprising to find that Rodewald observed that in the case of apples 

 and kohlrabi all the chemical energy of respiration appeared in the form of 

 heat, the estimated and observed values practically balancing. The differ- 

 ences observed by Bonnier between the calculated and actual amounts of 



1 Cf. Nathansohn, Mittheil. a.d. zool. Station zu Neapel, 1902, Bd. xv, p. 655. 



8 See Buchner, Die Zymasegahrung, 1903, where all the latest literature is collected. 



* The production of differences of potential enables particular partial functions to continue for 

 a time in the absence of oxygen. 



* Cf. Pfeffer, I.e., 1892, p. 201. 



