UPPER THERMAL DEATH POINTS 431 



range of temperature, or they were removed, a few at a time, at 

 the proper intervals with a capillary pipette. 



Where a gradual rate of temperature increase w^as desired, the 

 same general methods were employed except that the animals, 

 instead of being introduced suddenly into the test-tubes, were 

 placed in them at room temperature and the whole apparatus 

 was heated at the desired rate, samples of the animals being 

 removed, usualh^ at half-degree intervals. The animals, w^hether 

 suddenly or gradually exposed, were kept under observation 

 after removal in Syracuse watch-glasses until they had either 

 died or recovered, which in some cases required as much as 

 twenty-four hours, although as a rule their behavior when first 

 examined left little doubt as to the ultimate outcome of the 

 experiment. 



3. METHOD OF ESTIMATING ACCLIMATIZATION 



The extent to which acclimatization occurs during a slow rise 

 of temperature may theoretically be estimated by first finding 

 by method 1 (where there is no opportunity for preliminary 

 acclimatization to occur) the amount of injury inflicted in unit 

 time at the various temperatures passed through during the 

 rise, and in them adding together these separate injuries, be- 

 ginning with the lowest temperature, and taking into account 

 the duration of each, until a total just sufficient theoretically to 

 cause death is arrived at. The point at which this total is 

 reached is compared with the observed death point in the case 

 of the gradual rise. If the two points practically coincide, it 

 may be said that there is no evidence of acclimatization. If, on 

 the other hand, the observed death point is higher than the 

 calculated one, the presumption is that acclimatization has 

 occurred and the amount of the latter can be estimated, roughly 

 at least, in quantitative form. It must be remembered, of 

 course, that the calculated death point cannot be determined by 

 merely adding the theoretical amounts of injury at, for example, 

 34°, 35°, 36°, etc., since the rise does not proceed by a series of 

 sudden jumps, but continuously. Since, however, the relation of 



