1892.] NATURAL SCIENCKS OF PHILADELPHIA. 459 



If any body or mass of matter, living or dead, be placed anywhei-e 

 in space in order that its configuration may be changed, the neces- 

 sary energy and consequent motion competent to do so must be 

 developed : — 



(a.) By a physical change in some part of the substance of the 

 mass itself, or, 



(b.) The necessary energy competent to change the configuration 

 of the mass must be developed in material bodies, external to the 

 mass itself, or, 



(c.) Part of the energy necessary to produce a change in the con- 

 figuration of the mass must be developed by a physical change in a 

 portion of the substance of the mass itself, in conjunction or simul- 

 taneously with an energy, or energies, developed by a mass or body, 

 masses or bodies, external to itself. These? three are the only possi- 

 ble conditions. 



But, since all masses, living or dead, at the earth's surface are 

 known to be subject to the action of forces developed within them- 

 selves, as well as forces developed external to themselves, the third 

 condition (c) holds for all masses living or dead. 



Therefore the conclusion is that no mass at the earth's surface, 

 either living or dead, can by any thinkable possibility change its 

 own configuration, except under the condition that a combination of 

 internally and externally developed forces, agencies or energies 

 shall cooperate to that end. In other words, there can be no change 

 of configuration of a body without the expenditure or dissipation 

 of energy. 



Now, for the application of these known principles. 



Since variations of configuration, no matter whether they affect 

 the adult organism or its early stages, imply variations in the oper- 

 ation of internally and externally developed forces or energies 

 competent to produce such changes of configuration, it follows that 

 all changes in the forms of organisms involve the expenditure of 

 energy. In other words, all variations in the configuration of 

 organisms must be dynamically caused. This is true for the follow- 

 ing reasons : No variation in the configuration, either transient or 

 permanent (and therefore, inheritable) of a living body, can be pro- 

 duced without the cooperation of internally developed motions, 

 consequently, of energies, with externally developed energies or 

 such as are derived from the external world. Whether these coop- 

 erating energies are measurable or not, it is simply impossible for 



