4 The Mechanistic Conception of Life 



Mendel's law of heredity). Biology as far as it is based on 

 these two principles cannot retrogress, but must advance. 



II. THE beginning OF SCIENTIFIC BIOLOGY 



Scientific biology, defined in this sense, begins with the 

 attempt made by Lavoisier and Laplace (1780) to show 

 that the quantity of heat which is formed in the body of a 

 warm-blooded animal is equal to that formed in a candle, 

 provided that the quantities of carbon dioxide formed in both 

 cases are identical. This was the first attempt to reduce 

 a life phenomenon, namely, the formation of animal heat, 

 completely to physico-chemical terms. What these two 

 investigators began with primitive means has been completed 

 by more recent investigators — Pettenkofer and Voit, Rubner, 

 Zuntz and Atwater. The oxidation of a food-stuff always 

 furnishes the same amount of heat, no matter whether it 

 takes place in the living body or outside. 



These investigations left a gap. The substances which 

 undergo oxidations in the animal body — starch, fat, and 

 proteins — are substances which at ordinary temperature are 

 not easily oxidized. They require the temperature of the 

 flame in order to undergo rapid oxidation through the oxygen 

 of the air. This discrepancy between the oxidations in the 

 living body and those in the laboratory manifests itself also 

 in other chemical processes, e.g., digestion or hydrolytic 

 reactions, which were at first found to occur outside the 

 living body rapidly only under conditions incompatible with 

 life. This discrepancy was done away with by the physical 

 chemists, who demonstrated that the same acceleration of 

 chemical reactions which is brought about by a high tempera- 

 ture can also be accomplished at a low temperature with the 

 aid of certain specific substances, the so-called catalyzers. 

 This progress is connected pre-eminently with the names of 

 Berzelius and Wilhelm Ostwald. The specific substances 



