STRUCTURES RESEMBLING ORGANIC GROWTHS. 165 



sumed that in a similar manner an actively growing region has a 

 different potential from a quiescent region, and that the circuit 

 which includes this active region influences processes in the 

 tissue at a distance. Mathews found the regenerating end of a 

 Tubularia stem negative relatively to other regions (in the same 

 sense in which an active or injured region of, e. g., a nerve fiber 

 is negative; i. e., within the living element the positive stream 

 flows away from the active region) ; and he points out the 

 possibility that the current thus traversing the tissue may in- 

 fluence metabolic and other physiological processes at different 

 regions along its course, and thus may be an important factor in 

 the initiation and coordination of the formative or other activities 

 concerned in regeneration. 1 With this general conception I am 

 in full agreement. The experiments described above show in 

 how sensitive a manner the rate of formation of precipitation 

 structures responds to variations in the intensity and direction 

 of the local electrical currents traversing the system; and the 

 structural and other conditions in living systems are sufficiently 

 like those in the artificial models to warrant the belief that 

 electrical currents must influence in a similar manner the physio- 

 logical formative processes. The closeness of many of the above 

 parallels between the behavior of the two classes of systems 

 confirms this belief. 



It should be emphasized that the mode of transmission which 

 prevails in processes of growth and development appears to be 

 fundamentally of the same nature as the mode of transmission 

 of the excitation-state in irritable and conducting tissues like 

 muscle and nerve. I have dealt with the special features of this 

 latter mode of transmission in a recent series of papers in the 

 American Journal of Physiology. 2 In this case the bioelectric 

 circuit between the active and the inactive regions of the irritable 

 element appears to be responsible for the transmission of the 

 physiological effect; the current traversing the adjoining resting 



1 Cf. Mathews, loc. cit., p. 299. The following quotation from Pfeffer's " Physiol- 

 ogy of Plants" is also apposite here: "Weak electric currents continually circulate 

 in plants"; these are "partly maintained by chemical and physical agencies at 

 work in the plant itself. It is possible that these currents may influence meta- 

 bolism," etc. (English translation, Vol. 2, p. 106.) 



2 Amer. Journ. Physiol., 1914, Vol. 34, p. 414; 1915, Vol. 37, p. 348; 1916, Vol. 

 41, p. 126. 



