RELATION BETWEEN TEMPERATURE AND GROWTH 453 



condition of rest, but a dynamic condition of equilibrium, 

 and it will offer little effective resistance to excitatory con- 

 traction. We shall therefore expect that in growing organs 

 similar stimuli will induce responsive effects varying in pro- 

 portion to the changes of excitability in the tissue, under 

 different conditions. 



We saw, in the case of Crinuui Lily, that the optimum 

 temperature was near 35° C, and that at this optimum the 

 rate of growth was something like one and a half to three 

 times as great as at 30° C. At 37° C. we saw, further, that 

 the rate of growth was again reduced, and had become equal 



that, on recording the retardation of growth in response to 

 external stimulus at three definite temperatures, say 30° C, 

 35° C, and Z7° C., we should find it to be greatest at 35° C. 

 being in fact at that point about one and a half to three 

 times as great as at 30° C. The response at 37° C, on the 

 other hand, which is beyond the optimum, would be much 

 less than at 35° C, being equal to, or even less than, that at 



30° C. 



Table showing Variation of Excitatory Mechanical Response 

 AT Different Temperatures 



I have made numerous experiments completely bearing 

 out these conclusions. The mode of experimental proce- 

 dure is as follows : a balanced record is taken at the given 

 temperature, and the growing organ is then subjected to a 

 definite intensity of stimulation, which may consist of tetanic 

 thermal or electrical shocks, lasting for twenty seconds. 

 Records are then made of the resulting contractile retarda- 



