CHAPTER II. 



ENERGY IN BIOLOGY. 



§ I. Energy in Living Beings. — § 2. The First Law of Biological 

 Energetics: — All Vital Phenomena are Energetic Trans-' 

 formations.— § 3. Second Law : — The Origin of Vital 

 Energy is in Chemical Energy. Functional Activity and 

 Destruction.— § 4. Third Law:— The Final Form of 

 Energatic Transformation in the Animal is Thermal 

 Energy. Heat is an Excretum. 



The theory of energy was thought of and utih'zed in 

 physiology before it was introduced into physics, in 

 which it has exercised such an extraordinary influence. 

 Robert Mayer was a physicist and a doctor. Helm- 

 holtz was equally at home in physiology and in physics. 

 From the outset both had seen in this new idea a 

 powerful instrument of physiological research. The 

 volume in which Robert Mayer expounded, in 1845, 

 his remarkable views on organic movement in relation 

 to nutrition, and Helmholtz' commentary leave us in 

 no doubt in this respect. The essay on the mechanical 

 equivalent of heat, of a more particularly physical 

 character, is six years later than the earlier work. 



The Relations betzveen Energetics and Biology. — 

 The theory of energy is therefore only returning to 

 its cradle; and to that cradle it returns with all the 

 sanction of physical proof, as the most general theory 



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