AUTHORS ABSTRACT OF THIS PAPER ISSUED 

 BY THE BIBLIOGRAPHIC SERVICE, DECEMBER 9 



ACCLIMATIZATION AS A FACTOR AFFECTING THE 



UPPER THERMAL DEATH POINTS OF 



ORGANISMS 



M. H. JACOBS 



University of Pennsylvania 



1. INTRODUCTION 



The question of the effects produced on organisms by high 

 temperatures is one which has received the attention of biologists 

 for many years. The older workers were interested chiefly in the 

 determination of the so-called 'upper thermal death points.' 

 A resume of their observations is given by Davenport ('97). In 

 more recent times, the importance of the time factor, overlooked 

 in this earlier work, has been recognized, and modern investi- 

 gators have been more concerned with 'temperature coefficients' 

 (Putter, '14; Kanitz, '15) and with the possible causes of injury 

 at the elevated temperatures. In most of the recent, and in 

 practically all of the older work, however, a factor not sufficiently 

 taken into account is the method by which the temperatures used 

 in the experiments have been attained. 



There are, in general, three chief ways of bringing an organism 

 to a given high temperature. 1) The change may be practically 

 instantaneous, as, for example, if a minute animal in a small 

 quantity of water is suddenly expelled from a pipette into a 

 large volume of water at the required temperature. 2) The 

 change may be gradual, but uniform, as, for example, if the 

 animal is placed in a vessel of water at room temperature, 

 and heat applied in such a way that the rise per minute remains 

 constant until the desired point is reached. 3) The change may 

 be gradual, but at a constantly decreasing rate, as, for example, 

 if the animal is placed in a test-tube containing water at room 

 temperature, and the test-tube is then plunged into a large 



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