498 STUDIES IN GENERAL PHYSIOLOGY 



and pathology demand that the systematic development of 

 comparative physiology be one of the physiological problems 

 of today. 



I may be pardoned for calling attention to one special field 

 of comparative physiology which I believe to be especially 

 fertile. I refer to the field of physiological morphology. 

 I applied this name to the investigation of the connection 

 between the chemical changes and the process of organiza- 

 tion in living matter. Two series of facts allow us to connect 

 these two groups of phenomena: (1) the fact that phenomena 

 of fermentation lead to an increase in the number of mole- 

 cules, and thus bring about an increase of osmotic pressure in 

 the cells, this increase of osmotic pressure being the source 

 of energy for the work of growth ; (2) the facts of hetero- 

 morphosis, i. e., the possibility of transforming in certain 

 animals one organ into another or substituting one organ for 

 another through external influences, such as gravitation, con- 

 tact, light, etc. 



The exact and definite determination of life-phenomena 

 which are common to plants and animals is only one side of 

 the physiological problem of today. The other side is the 

 construction of a mental picture of the constitution of living 

 matter from these general qualities. In this portion of our 

 work we need the aid of physical chemistry and especially of 

 three of its theories: stereochemistry, Van 't Hoff's theory 

 of osmotic pressure, and the theory of the dissociation of 

 electrolytes. We know that the peculiar phenomena of oxi- 

 dation in living matter are determined by fermentative pro- 

 cesses, and we venture to say that fermentations form the 

 basis of all life-phenomena. It has been demonstrated that 

 fermentability is a function of the geometrical configuration 

 of the molecule. Saccharomyces cerevisicv is a ferment for 

 such sugars only as have three or a multiple of three atoms 

 of carbon in the molecule. Among the hexaldoses only 



