X INFLUENCE OF TEMPERATURE ON BIOLOGICAL SYSTEMS 



After a flourishing period of temperature studies that resulted, between 

 two and four decades ago, in the accumulation of a fairly voluminous 

 literature, interest began to wane. It seemed that this approach, while 

 certainly not exhausted, held a diminishing promise of advances in any 

 real understanding. Research with pressure had independently reached a 

 similar impasse. It was not until around 1935 that certain new results in 

 theory and experiment, as mentioned presently, removed some stumbling 

 blocks in the way of further progress and laid a common basis in a rational 

 chemical theory for the biological effects of both temperature and pressure. 



At almost the same time that Arrhenius published his rate theory, 

 Regnard published, in 1891, the first monograph dealing with the influence 

 of increased hydrostatic pressures on biological processes. Interest in the 

 physiological effects of pressure stemmed from the discovery, on the 

 dredging expedition of the Talisman in 1882-1883, of living organisms at 

 depths of 6,000 meters in the sea, where the pressure amounts to about 

 600 atmospheres or nearly 9,000 pounds per square inch. The early ex- 

 periments, principally by Regnard and by his contemporary Certes, in- 

 volved pressures only within the range from 1 to 600 atmospheres, and it 

 is aproximately this range, i.e. up to about 1,000 atmospheres, that turns 

 out to be most significant from a physiological point of view. Within this 

 range, compression frequently results in large and easily reversible changes 



in activity. 



Unfortunately, the studies begun by Regnard and Certes have been 

 carried further by relatively few investigators, and the emphasis in re- 

 search with pressure has tended in the direction of higher and higher 

 pressures, upwards of 5,000 atmospheres, which cause irreversible, de- 

 structive effects such as the denaturation of proteins, inactivation of 

 viruses and killing of bacteria. Moreover, very little work has yet been 

 done with organisms indigenous to the deep sea, so the problem that in- 

 spired the first biological research with pressure remains virtually un- 

 touched except by implication of results that have been obtained with 

 material from terrestrial sources. The implications of studies on terrestrial 

 forms, however, can be remarkably enlightening, as several papers in this 

 volume illustrate. 



For nearly half a century after the appearance of Arrhenius's theory 

 and Regnard's monograph, three stumbling blocks remained in the road 

 toward understanding the physiological effects of pressure and tempera- 

 ture. First, there was no explicit theory for the quantitative relation be- 

 tween pressure and chemical reaction rates. Second, it was not realized that 

 the physiological effects of increased pressure are subject to profound 

 modification, even reversal, by temperature. Third, no clear evidence was 



