24 LAW OF THE CONSTANCY OF ENERGY. 



such as the movement of the entire body, of the extremities and many 

 of the viscera; also appreciable even microscopically in cells. 



2. As movement of the atom: in the form of heat. As is well known, 

 the vibration of atoms results in the production of heat or of light or 

 in chemically active waves in accordance with the number of vibrations 

 in the unit of time. The smallest number of vibrations are those of 

 heat, the highest those that are chemically active, and between the. 

 two are the vibrations of light. In the human body only heat-waves 

 have of these three been observed, but some lower forms of life are 

 capable of causing also luminous phenomena. 



In the human organism movements in mass are constantly trans- 

 formed in certain organs into heat, as, for instance, the kinetic energy 

 in the circulatory organs, and which is transformed into heat by the 

 resistance within the vascular apparatus. The measure of these trans- 

 formations also is the unit of energy = i grammeter, and the unit of 

 heat = 425.5 grammeters. 



3. In the form of potential energy (latent energy) the organism con- 

 tains many chemical combinations characterized especially by great 

 complexity of constitution and imperfect saturation of the contained 

 affinities, and, therefore, by their great tendency to break down into 

 simpler bodies. The body is capable of generating both heat and 

 kinetic energy from potential energies; kinetic energy, however, is always 

 in combination with heat, while heat may be produced alone. The 

 simplest measure of the potential energies is the amount of heat that 

 can be obtained by the combustion of the chemical bodies in question 

 representing the potential energy. As a secondary matter the number 

 of equivalent units of energy can be determined in turn from the amount 

 of heat generated. 



4. It is known that the phenomena of electricity, magnetism and 

 diamagnetism, may make themselves manifest in two directions, namely, 

 in the form of movement of minutest particles, which may be recog- 

 nized in the incandescence of a thin wire (the seat of great resistance) 

 traversed by a strong current; and also in the form of movement in 

 mass, as exhibited in the attraction or repulsion of the magnetic needle. 

 In the body electric phenomena appear in the muscles, nerves, and glands ; 

 but as compared with other forms of energy they are of subordinate 

 importance. It is not improbable that the electric energy of the body 

 is transformed almost wholly into heat. The endeavor to obtain a 

 measure for electric energy, the unit of electricity, as a means of direct 

 comparison with the heat-unit and the unit of energy, has likewise been 

 attended with definite success. 



Luminous phenomena do not occur in the bodies of the most highly 

 developed animals. The significant investigations of Hertz have shown 

 that the phenomena of light exhibit the greatest analogy with those of 

 electricity in the most important connections, so that the relations be- 

 tween the two forms of energy must accordingly be admitted. 



It is certain that in the body also the different forms of energy can 

 be transformed one into another in a definite and constantly invariable 

 degree, and that new energy never develops spontaneously in the body, 

 while that present is never destroyed ; and thus also the organisms are 

 a theater in which the law of the constancy of 'energy is in unceasing 

 operation. 



