ANIMALS AND PLANTS. 25 



The original statement of Julius Robert v. Mayer may be appropriately quoted 

 at this point: "There is but one energy, which operates with unceasing change in 

 dead and in living things, and nowhere in either does any change take place 

 without alteration 'in the form of energy. Physics has but to investigate the 

 metamorphoses of energy, as chemistry has to investigate the transformations of 

 matter. The generation as well as the destruction of energy is beyond the range 

 of human thought and action: Nothing comes from nothing, nothing can give rise 

 to nothing. If chemistry teaches the immutability of matter, then it is the obliga- 

 tion of physics to demonstrate the quantitative immutability of energy notwith- 

 standing all variability in form. Gravitation, motion, heat, magnetism, electricity, 

 chemical difference, are all but varying modes of manifestation of one and the 

 same natural force that reigns throughout the universe, for any one can under 

 special conditions be converted into another." (Lucretius Carus, born 95 B. C., 

 had already said: "Nullam rem a nihilo gigni, .... neque ad nihilum 

 interimat res.") 



ANIMALS AND PLANTS. 



Locked up in the constituent elements of the animal body is an 

 aggregation of chemical potential energies (Lavoisier, 1789). The total 

 amount of these in the human body could be measured if the entire 

 cadaver were completely burned in a calorimeter and the number of 

 heat-units generated were noted as a result of its combustion. The 

 chemical combinations in which are bound up the potential energy are 

 characterized by complexity in the arrangement of their atoms, by 

 imperfect saturation of the affinities of the atoms, by a relatively small 

 oxygen-content, and by a great tendency to and readiness of disintegra- 

 tion. 



It may be conceived that food is withheld from an individual. The 

 fasting person loses hourly 50 grams of body- weight; the tissues in which 

 his potential energy is bound up are thus consumed. Through the 

 taking up of oxygen combustion continually takes place, and as a 

 result of this process the complex elements of the body are converted 

 into simpler ones, whereby the potential energy forming the connecting 

 link between them is transformed into kinetic energy. It is a matter 

 of indifference whether the process of combustion takes place rapidly 

 or slowly; the same amount of chemical matter always yields the same 

 amount of kinetic energy, as, for instance, heat. After the lapse of 

 a certain time the fasting person becomes conscious of the state of 

 threatened exhaustion of his stored potential energy, and the condi- 

 tion of hunger sets in. The hungry person takes food; all food for the 

 animal kindgom is derived either directly or indirectly from the vege- 

 table world. Even carnivorous animals, which eat the flesh of other 

 animals, consume in the final analysis organized material formed from 

 vegetable food. Thus, the existence of the animal kingdom necessarily 

 implies unconditionally the previous existence of the vegetable king- 

 dom. 



Vegetable structures thus contain all of the nutritive materials 

 necessary for the animal body. In addition to water and inorganic 

 matters, vegetables contain, among other organic combinations, espe- 

 cially also the three principal representatives of nutrient bodies, namely, 

 fats, carbohydrates, and proteids. All of these are the seat of abundant 

 potential energy in accordance with the complexity of their chemical 

 constitution. 



