426 PROCESSES INFERRED FROM INDIRECT OBSERVATION 



suffice to coagulate Proteins. For example, Goodspeed, who investi- 

 gated the thermal death of barley-seeds, exposed them to temperatures 

 ranging from 55 to 70 C. and obtained a temperature-coefficient of 

 10 for the duration of life, a coefficient which is very close to the value 

 8 obtained by Chick and Martin in estimating influence of tempera- 

 tures of similar magnitude upon the rate of coagulation of Hemoglobin. 



The remarkable disparity between the effects of temperature upon 

 the Life-duration and the Development of organisms has been applied 

 by Loeb to the explanation of what would otherwise be an exceedingly 

 puzzling fact, namely the extraordinary density of the population of 

 the polar seas. In his account of the Valdivia expedition, Chun 1 calls 

 especial attention to the quantitative difference in the surface fauna 

 and flora of polar and temperate or tropical regions : " In the icy water 

 of the Antarctic, the temperature of which is below C, we find an 

 astonishingly rich animal and plant- life. The same condition with 

 which we are familiar in the Arctic seas is repeated here, namely, that 

 the quantity of plankton material exceeds that of the temperate and 

 warm seas." And again, in describing the pelagic fauna in the region 

 of the Kerguelen Islands he states: "The ocean is alive with trans- 

 parent jellyfish, Ctenophores (Eolina and Callianira) and of Siphono- 

 phore colonies of the genus Agalina." 



This observation, which has been repeatedly made by Arctic and 

 Antarctic travellers, would appear paradoxical in consideration of the 

 effect of temperature upon development, for the rate of development 

 of organisms is, as we have seen, halved or even reduced to a greater 

 extent by a drop of 10 C. in temperature. When, however, we reflect 

 that the duration of life of these slowly developing organisms is pro- 

 longed a thousandfold, the density of the polar population becomes 

 explicable, for the net result of these opposed effects would be a great 

 increase in the number of surviving individuals and in the number of 

 successive generations simultaneously inhabiting the cold waters. 



The temperature-coefficient of the life-processes which we have 

 hitherto considered have all been of such a magnitude as to clearly 

 invite the supposition that the velocities of the phenomena are deter- 

 mined by the rate at which underlying chemical transformations occur. 

 We now come to a life-phenomenon of peculiar character in which the 

 testimony of the temperature-coefficient is far from being so unequivo- 

 cal, namely the Conduction of Stimuli along the fibers of a motor-nerve. 



The influence of temperature upon the rate of conduction of the 

 nervous impulse was first investigated by S. S. Maxwell, who employed 

 for this purpose the pedal nerve of a large slug, Ariolimax columbianus. 

 This nerve was selected on account of its considerable length and the 

 slowness of the propagation of the impulse permitting a much greater 

 exactitude of measurement than is possible in the shorter and more 



1 Cited after J. Loeb: The Mechanistic Conception of Life. 



