530 THE THEORY OF ENERGY AND THE LIVING WORLD. 



discover other forms and specific varieties of energy"? jSTot at all. Such 

 an affirmation would be at once as ambitious as imprudent. The his- 

 tory of the physical sciences ought to render us more circumspect. It 

 teaches us that little more than a century has passed since electrical 

 energy has made its entrance upon the scene, and we have commenced 

 to know this form of energy. Such a discovery as this, right under our 

 eyes, of an agent playing such an important part in nature should leave 

 the door open in the future for other surprises. 



This reservation is of great importance from the point of view of the 

 arrangement of the phenomena of life in the universal science of ener- 

 getics. It allows us to admit that in addition to those forms of energy 

 which are common in the physical world, other varieties may be met 

 with in the living organism such as are peculiar to it. These are still 

 too little known to be sought out elsewhere; but doubtless they exist 

 also in the physical world, and will come to light when our means of 

 investigation shall have become sufficiently advanced. At present we 

 must admit their possibility to account for the peculiarity of some of 

 the phenomena of life which are quite special and different from those 

 of physics. With this precaution we recognize at once wherein the 

 vital phenomena reduce themselves to the domain of universal physics, 

 and wherein a provisional separation still remains. We thus escape 

 the charge of gross materialism incurred by Descartes and Boerhave, 

 those uncompromising scientists who thought to discover in the actual 

 instruments of our laboratories the model of all mechanisms, even the 

 most complex, of animal life; a proposition as vain as it would have 

 been for an iatro-mechanician to have tried to explain before the time 

 of Lavoisier the elementary phenomena of respiration or the phenom- 

 ena of the excitation of the nerves before Volta. 



But on the other hand we must recognize the profound truth lying 

 behind this extreme and unfortunate realism, which, acting through an 

 obscure and common instinct, has constrained the biologists of all 

 times to attempt to bring the phenomena of life under the empire of 

 general physics. 



We now know with certainty that many forms of energy are common 

 to the living and physical worlds, and these energies — chemical, ther- 

 mal, and mechanical — retain their character of mutability, their scale 

 of equivalence, and their states of being, actual and potential. 



If it shall happen again, as it happened in the last century in regard 

 to electricity, that some unrecognized form of energy is suggested by 

 physiological researches, we can affirm in all confidence that this new 

 energy will obey no new laws. It will be governed in its transforma- 

 tion into the known forms by the rules already determined; it will 

 appertain to the universal order as well as to life, and it will be a con- 

 quest for general physics as well as for biology. It can easily be 

 understood after these explanations of the significance and portent of 

 that affirmation, which is the foundation of biological energetics, that 



