HEREDITY FROM PHYSICO-CHEMICAL POINT OF VIEW. *]\ 



The general physiological problem presented by the phenomena 

 of growth and heredity thus reduces itself to these terms: what 

 are the essential physico-chemical conditions upon which this 

 power of specific construction depends? It seems clear that 

 only a thorough knowledge of the conditions determining the 

 special type of metabolism involved in the process, and especially 

 of its constructive side, can answer such a question. The living 

 organism or cell is primarily a metabolizing system. Growth 

 is the expression or result of a process of metabolism; both the 

 material and the energy required for growth come from outside; 

 within the organism they are transformed in such a manner as to 

 build up an organized system of predetermined kind, the seat of 

 chemical and physical processes which maintain the system and 

 enable it under appropriate conditions to increase in size or to 

 produce other similar systems leading independent life. 



In all organisms constructive metabolism involves the syn- 

 thesis of a multiplicity of new chemical compounds from the 

 food and other materials furnished by the surroundings. The 

 food-materials are typically non-specific in their chemical nature, 

 i. c., they show no relation to the specific character of the or- 

 ganism utilizing them; they are either chemically simple in them- 

 selves, or become so during incorporation. In animals, where 

 the organism receives part of its food in highly specific form, as 

 protein, all specificity is invariably lost in the hydrolytic proc- 

 esses of digestion; the material before becoming available for 

 nutrition is reduced to a form in which it can be utilized indif- 

 ferently by all cells. This non-specificity of the food-materials, 

 as they reach the cells, is in striking contrast with the specificity 

 of the compounds built up from them within the cells. Reduc- 

 tion to a simple or non-specific state is thus the indispensable 

 preliminary to the constructive process. It is therefore highly 

 significant that the chief structural colloids, the proteins, are 

 so readily transformed from the specific to the non-specific state. 



by which it grows and reproduces itself. Organic synthesis, generation, regenera- 

 tion, maintenance, healing of wounds, are different aspects of an identical phe- 

 nomenon, are varied manifestations of the same agent. ..." In the Presidential 

 address of J. S. Haldane before the British Association in 1908 (Nature, Vol. 78, 

 p. 555) a similar point of view is expressed, e. g. " nutrition itself is only a constant 

 process of reproduction .... Heredity is for biology an axiom and not a problem." 



