HEREDITY FROM PHYSICO-CHEMICAL POINT OF VIEW. 8 1 



down of organized material, and apparently some disintegration 

 of cell-structure then always takes place, for protein metabolism 

 is increased even though slightly under good nutritive conditions 

 by increased muscular work. 1 Hence for normal regulation 

 of cell-activity it is essential that a compensatory or constructive 

 series of processes should be aroused into action by the same 

 conditions that stimulate or call forth the destructive or energy- 

 yielding activity. "Functional breakdown in living material 

 is itself the precursor and instigator of the renovation accom- 

 plished by the formative process, which works silently and ob- 

 scurely in the interior of the tissue" (i. e., without evident exter- 

 nal manifestation, in contrast to the destructive process). 

 "Losses are thus repaired as rapidly as they are caused, and 

 since equilibrium tends to re-establish itself as soon as it is de- 

 stroyed, the normal composition of the living body is main- 

 tained." 1 Bernard also recognizes that this process of restitution 



1 It is now amply demonstrated that increased muscular work in higher animals 

 leads to little or no increase in breakdown of protein (as indicated by N-excretion), 

 provided the non-nitrogenous food-constituents are sufficient in quantity, especially 

 the carbohydrates. If the food contains sufficient protein for maintenance, but 

 carbohydrate and fat are deficient, there may be a considerable increase in N- 

 excretion, but typically not enough to account for the increased energy-production 

 on the basis of oxidation of protein; in this case the surplus of energy comes from 

 the non-nitrogenous reserves of the organism. Carbohydrate is especially effective 

 as a protein-sparer, a fact indicating that in the construction of protein it plays 

 an essential part. It is also the chief source of muscular energy; and the fact 

 that vigorous muscular work, involving active consumption of sugar, is the chief 

 condition for the normal growth of the tissue, shows that the energy required for 

 this growth i. e. for the chemical and structural syntheses involved is derived 

 from the oxidation of sugar. The possible metabolic changes concerned in this 

 process cannot be considered in an article like the present. But that carbohydrate 

 is essential for the assimilation of amino-acids and other nitrogen compounds in 

 both animals and plants is indicated by a large body of recent and older investi- 

 gation. Thus for the assimilation of amino-acids by yeast and moulds sugar is 

 indispensible (of. the series of papers by F. Ehrlich, Biochem. Zeitschr., 1906, Vol. I, 

 p. 8; 1908, Vol. 8, p. 438; 1909, Vol. 18, p. 391; 1911, Vol. 36, p. 477); similarly 

 in higher plants the synthesis of protein from amides in germination requires the 

 presence of carbohydrates (for a brief summary of the facts cf. Jost's "Physiology 

 of Plants," p. 175). The work of Loewi, Liithje and others has shown the great 

 importance of carbohydrates in the synthesis of protein from amino-acids in higher 

 animals; there is also clear evidence that derangement of carbohydrate metabolism 

 (e. g., in pancreatic or other diabetes) interferes very directly with the synthesis 

 of protein (cf. Chapter 9 of Cathcart's "Physiology of Protein Metabolism" for a 

 general review of this subject and literature). 



2 "Lecons sur les phenomenes de la vie," Vol. i, p. 127. 



