46 THEORETICAL BIOLOGY 



It was more difficult to bring colours under mathematical 

 formulae : that became possible only when physicists assem- 

 bled under the concept of " light " the spatial influencing of 

 coloured surfaces on one another, and in addition discovered 

 the ether, a new medium, constructed on the analogy of air, 

 and transmitting light-waves. 



Newton had got out of the difficulty in a more primitive 

 manner, by assuming that little coloured spherules were pro- 

 jected through space. The ether, however, proved itself a 

 much better aid to the analysis of the action of light. 



As we have already shown, the subjective effects of colour 

 can never be referred to spatial laws, because they have laws 

 of their own ; and only a thorough-going separation of the 

 spatial laws of light from the subjective laws of colour can 

 obviate the confusion still prevailing in optics. 



With the help of the ether it also became possible to bring 

 under observation the spatial laws of heat. As concerns the 

 subjective laws of heat, we owe our information to Johannson. 

 Heat consists of three qualities — warm, cold and hot. If part 

 of our skin is touched simultaneously by two objects, one of 

 which calls forth the sensation " warm " and the other that of 

 '* cold," the sensation " hot " results. 



From this we may conclude that we have only two nerve- 

 ending apparatuses in our skin — one for warm and one for 

 cold, — and that the combined simultaneous stimulation of 

 both produces " hot." Of this subjective law, the physicist 

 knows nothing, and moreover it is not necessary that he 

 should ; he is concerned with investigating the radiation of 

 heat, — i.e. with etheric vibrations or the conduction of heat. 



As regards the phenomenon of smell, the theory of 

 emergent, chemically active spherules is still held, because 

 the air-currents determine their path. Their subjective 

 effects, i.e. odours, consist, as with the qualities of taste, in 

 the drowning of one quality by another. 



