194 



The Plant World. 



for use? Any answer to this question involves a study of those 

 physiological processes collectively called respiration. It in- 

 volves at least the quotation of physics and chemistry; and ex- 

 perience causes me sincere regret that not more botanists are at 

 least potentially physicists and chemists. 



The calorific values of the ordinary fuels and of the usual 

 foods have been determined with a fair degree of precision. 

 These values are found by experiments involving the complete 

 oxidation (combustion) of the materials in question. A pound 

 of a certain kind of coal will yield, under certain carefully speci- 

 fied conditions of firing, so many units of heat. The products 

 of the combustion will be CO2, H2O, small amounts of various 

 other volatile substances, ash, and heat. Similarly the calorific 

 values of starch, sugar, fat, oil, protein (meat), et cetera, have 

 been determined outside of the body. These determinations, 

 however, involve the comparatively simple, or at least the com- 

 paratively isolated, processes of the laboratory. They can not 

 include the multitude of processes, great and small, going on, 

 in more or less orderly fashion, in the most confusing thing in 

 existence, the living body. These determinations assume that 

 all the energy liberated by combustion is liberated in the form 

 of heat. This assumption is doubtless correct so far as the 

 laboratory determinations are concerned; but it is probably a 

 mistake to apply it to physiological oxidation. Taking this for 

 granted, and seeing a little more plainly that the apparently 

 simple question above, regarding the yield of energy in respira- 

 tion, is not to be answered offhand, I should like to limit myself 

 to the question whether a fair part of the energy yielded is avail- 

 able for use, or whether much of it is lost. 



The study of heat production in respiration, which I have 

 been carrying on for a year, leads me to believe that respiration 

 is a very wasteful process if the liberation of energy in the form 

 of heat is all there is to it. For example, using 80 grams of 

 soaked peas, washed in an antiseptic solution to prevent bac- 

 terial action, in each of five silvered Dewar flasks, I found that 

 the temperature roseover 100 p.c. within three days in each flask.* 

 The silvered flasks act only as remarkably efficient insulators, 

 retaining in the peas and within the flasks a very high proportion 



•Peirce, G. J. A new respiration calorimeter. Botanical Gazette, 46, 1908. 



