416 PROTOPLASM 



and Perrin have suggested that all chemical reactions are photo- 

 chemical in character. They assume that a molecule does not 

 react until it becomes activated by radiant energy. This 

 assumption — that every simple chemical reaction is accomplished 

 by the adsorption of light of one frequency — involves also 

 the assumption that light of another frequency is emitted. 

 The hypothesis enabled Perrin to give an explanation of the 

 phenomena of photo- and thermoluminescence. While it is 

 unlikely, as G. N. Lewis says, that all chemical reactions are 

 due to the influence of light and not in part to molecular activity 

 (thermal motion), it seems very likely that the emission of light 

 is a frequent characteristic of chemical reactions. Solidified 

 nitrogen emits an intense luminescence when exposed to electric 

 rays ; thus does a single chemical element have the properties of a 

 phosphorescent body. 



F. Daniels, in a discussion of photons in chemistry and biology, 

 states that, as the phenomenon of chemical luminescence is of 

 not infrequent occurrence in nature (in decaying wood, bacteria 

 in sea water oxidized as a boat plows through the water, etc.), 

 there is no fundamental reason why some reactions in protoplasm 

 should not emit photons. Any chemical reaction that gives 

 rise to the displacement of an electron (or atom) in a molecule 

 will cause a photon of radiation to be emitted when the electron 

 falls back into its position of lower energy. 



The emanation of radiant energy from living matter in the 

 form of ultraviolet light (which is said to be the nature of Gur- 

 witsch rays) is no more remarkable than the giving off of heat, 

 light, and electricity by organisms. Because these latter are 

 of such common experience, we unhesitatingly admit their 

 existence. It is but a step from heat, light, and electricity to 

 such other forms of radiant energy as ultraviolet rays, roentgen 

 rays, radium radiations, and cosmic rays. While certain of 

 these manifestations of energy are less well understood than 

 others, and in this sense are more mysterious, yet none is vitalistic 

 except in so far as it is given off by living matter. From every 

 point of view, each of them is as physical — as materialistic — 

 as are the others. The presence of radiant energy in proto- 

 plasm is one of the least mysterious things about it. We 

 need think only of movement, growth, and reproduction to 

 realize this. 



