CONTRIBUTION TO THE THEORY OF SCIENCE 235 



Accordingly it would seem possible to construct a table of all the 

 possible forms of energy by assigning to the factors of energy all pos- 

 sible manifoldness characteristics and combining them in pairs, with 

 the subsequent elimination of the products which do not conform 

 to the conditions stated on p. 234. By comparison with all the forms 

 of energy known at the time, it would be possible to discover the forms 

 that were still unknown and to outline their most important properties. 

 Experience would merely have to discover their specific constants. 

 For some years I have myself from time to time attempted to carry out 

 this program ; but hitherto I have not progressed far enough to justify 

 the publication of the results already obtained. 



If now we turn to the biological sciences, the new phenomenon we 

 meet is life. If we limit ourselves to observable facts excluding all 

 hypotheses, we shall recognize as the universal characteristic of all life- 

 phenomena the stationary stream of energy which flows through a 

 comparatively constant structure. Metabolism is merely a part, 

 though a most important part, of this stream. Plants, particularly, 

 demonstrate immediately the paramount importance of energy in its 

 most immaterial form, the sunbeams. Self-maintenance and repair 

 with the production of similar descendants are other essential char- 

 acteristics. All these characteristics must be present in order that an 

 organism may arise. Furthermore they must be present if the know- 

 ing individual is to be capable of forming, by repeated experiences, a 

 concept of any given organism, say a lion or a mold. Other organisms 

 not fulfilling these conditions may occur. Because they are unique, 

 they do not lead to the concept of a species, but are excluded (except of 

 course for special purposes) from scientific consideration as ' malfor- 

 mations ' or ' monsters/ 



Whereas organisms mostly deal with forms of energy which are 

 familiar to us in the inorganic world, we find the higher forms pos- 

 sessed of organs which undoubtedly produce, or are active in, the trans- 

 formation of energy, though we do not know which form of energy 

 acts within them. These organs are termed nerves; and their func- 

 tioning is regularly of such a nature that upon the application of a 

 definite form of energy to one end, they call into action at the other 

 end forms of energy there present and which there act in their own 

 peculiarly characteristic way. That energetic changes do occur in the 

 process of nerve-transmission may be regarded as settled. We are 

 therefore justified in speaking of nerve energy, leaving the question 

 open as to whether it be a special form of energy or merely chemical 

 energy or lastly a combination of several forms of energy. 



While these processes of nerve stimulation with corresponding re- 

 action in the end-organ, a muscle, for example, may be observed ob- 

 jectively, we find within ourselves connected with this nervous process 



