UPPER THERMAL DEATH POINTS 439 



injury inflicted at the temperatures below 40° would not drop 

 off so rapidly, or, in other words, that the animals would be 

 more injured during their gradual rise by the time they had 

 reached 40°, and that consequently the calculated death tem- 

 perature would be even lower than before. But this would only 

 make stronger the evidence of acclimatization already obtained 

 by the rough calculation. 



It is of some interest not merely to show that acclimatization 

 occurs, but to attempt to express its extent in quantitative form. 

 This can be done in an approximate fashion by calculating the 

 area enclosed by the given curve up to = 44° and comparing 

 this area with that which represents unit injury, i.e., death. 

 Such results, of course, are only rough approximations, but have 

 nevertheless a considerable interest. Using the formula already 

 given : 



I = tln 



logeQl 



the area in the case just mentioned proves to be 44 units of 

 injury. In other words, before death occurred, during the 

 gradual rise, the animals had withstood about forty-four times 

 the usual fatal injury. It is suggested that in this and in similar 

 cases the excess in area enclosed by the curve of injury, up to 

 the point of death, over the area (taken as unity) which repre- 

 sents an amount of injury just fatal when the change is sudden, 

 may be called the surplus resistance, and be used as a rough 

 quantitative measure of the extent of acclimatization. In this 

 case the surplus resistance is equal to 43. The animals have, in 

 other words, added to their normal lives, so to speak, forty- 

 three additional lives by their ability to adjust themselves to 

 the changing environment. 



The favorable effect of a slow as compared with a rapid rise 

 of temperature on Paramecium is shown by another experiment 

 in which method 3 was combined with method 2. In this case, 

 a tube of very small caliber (3 mm.) with extremely thin walls 

 was prepared by drawing out the lower portion of a thin-walled 

 test-tube in a flame to a considerable length and sealing the small 



