PHTSIOLOGT 23 



temperature (if the temperature coefficients of 

 the reactions differ) or by chemical agents. The 

 same result might be brought about by physical 

 means, especially where structural changes 

 occur which alter the permeability of the plasma 

 membrane or of internal structures (such as the 

 nucleus and plastids) in such a way as to bring 

 together substances which do not normally react. 



The results obtained lead to a very simple 

 conception of life processes, namely that they 

 consist of a series of consecutive reactions. By 

 varying the speed of the different members of 

 the chain we can, without introducing any new 

 substance, profoundly influence the course of 

 events. In this way the effects of the most di- 

 verse stimuli on such processes as growth, differ- 

 entiation, reproduction, and irritable response 

 might be accounted for. 



The results obtained by the electrical method 

 have been confirmed by a variety of other 

 methods, as, for example, by the passage of 

 substances through diaphragms of living tissue. 

 In this case diffusion takes place principally be- 

 tween the cells, but as permeability increases it 



