JO SI AH WILLARD GIBBS 557 



investigation of soils. " The soil is the stomach of the plant/' being 

 in effect a complex system in three phases, of which the liquid phase 

 furnishes the nutrient solution to the plant. The bacteria, molds and 

 enzymes in the soil make its relation to the plant a complicated and 

 difficult problem,®^ but the application of physical chemistry to its solu- 

 tion of Cameron, Bell, Briggs and other chemists in the United States 

 Department of Agriculture is clearly in the right direction. Eecently 

 Bancroft has shown how the phase rule may be applied to photo- 

 chemistry when the radiant energy of absorbable light such as ultra- 

 violet is converted into chemical energy. The light acts as another 

 variable requiring n -{- 3 phases in an invariant system while in general 

 we may have as many additional degrees of freedom as there are kinds 

 of light.®^ The application of the phase rule to organic chemistry is 

 difficult owing to " passive resistance to change." Most of the reac- 

 tions in organic chemistry are reversible, i. e., proceed to equilibrium, 

 and if sufficient time be allowed will reverse backwards like a Carnot 

 cycle, to some approximation of their initial state. Many reactions 

 with organic substances, however, seem to stop short of equilibrium, and 

 the chemist, in working with colloids, ferments, gums, etc., is balked by 

 certain passive forces, which do not, like friction or viscosity, merely 

 retard chemical change, but actually prevent it. Even such explana- 

 tions as the hypothesis of reversibility in infinite time or Duhem's 

 theory of false equilibria and pseudoreversible reactions, do not entirely 

 account for these mysterious phenomena, and it is probably through 

 new methods of laboratory procedure that organic chemistry will ulti- 

 mately pass into the hands of the physical chemists. 



In physiological chemistry the doctrine of phases opens out a new 

 perspective, a new qualitative way of envisaging problems which, ap- 

 proached quantitatively, are a severe task even for an Emil Fischer. 

 Eecently the Dutch physiologist Zwaardemaker has proposed the ap- 

 plication of the phase rule and the second law to general physiology.** 

 " The task of an energetic histology," he says, " would be to give the 

 number of phases and their relations, while an energetic physiology 

 would determine the equilibria and reversible processes by direct experi- 

 mentation."^^ Zwaardemaker proposes to regard the human body at 

 rest as a complicated system of coexistent phases in equilibrium, the 

 metabolic, reproductive and other processes of which are irreversible. 

 The animal cell he holds to be a system of heterogeneous phases, the 

 equilibrium of which can be disturbed by experimental removal of the 

 nucleus. The red blood corpuscles are probably divariaut, four com- 

 ponent systems of four phases, while the endothelial cells of the ven- 



«- Cameron, ibid., 1904, VIII., 642^ ~ 



«3 Bancroft, ibid., 1906, X., 721. 



^ Zwaardemaker, " Ergebnisse d. Physiol.," Wiesbaden, 1906, V., 108. 

 ^Loc. cit., 154. 



