the Temperature of Liquid Hydrogen on Seeds. 367 



obliged to admit with Professor C. de Candolle and Messrs. Brown and 

 Escombe that it may descend to a purely static condition 1 



This is really bound up with another question. The kinetic condi- 

 tion depends on the constant liberation of energy by chemical change. 

 Of this the most important is that due to oxidation. But we now 

 know that this is not the only source of energy in living matter, or in 

 all cases the indispensable one. The late Dr. Eomanes showed that 

 neither a high vacuum nor subsequuent exposure for twelve months to 

 absolutely indifferent gases, such as hydrogen or nitrogen, or even 

 poisonous ones such as hydrogen sulphide, had any effect on the ger- 

 minative power of seeds. Professor Pfeffer has, however, informed me 

 in conversation that an injurious effect is ultimately produced. 



Vital processes have their optimum point as regards temperature. 

 Their superior limit for the reason already pointed out is tolerably 

 sharp; but the inferior is by no means equally so. According to 

 Boussingault the decomposition of carbon dioxide by green plants 

 may take place nearly at 0° C* Below the optimum there is then some 

 evidence of a "slowing down." While some processes reach their 

 limit, can we assume that all do ? 



The question would be peremptorily answered for us by those 

 who assert that all chemical action is in abeyance at such temperatures 

 as I am discussing. Photographic action still takes place at the 

 temperature of liquid air, though this may be due to phosphorescence. 

 But a jet of hydrogen will burn in. it. 



Messrs. Brown and Escombe sum up the two methods of explaining 

 what has been called " dormant vitality " with sufficient accuracy in 

 their paper. According to the one view, metabolic and its resultant 

 kinetic activity is " slowed down " indefinitely. In such a case as now 

 described, it might be said that this takes place along an asymptotic 

 curve, continually approaching but never becoming equal to zero. 



According to the other, protoplasm passes absolutely from the 

 kinetic to the static condition. Its locked-up energy becomes purely 

 potential, and Professor C. de Candolle has not hesitated under these 

 circumstances to compare it to an explosive. 



It has been pointed out that such a conclusion is absolutely in con- 

 flict with Mr. Herbert Spencer's well-known definition of life. But it 

 appears to me that that definition was only intended to apply to 

 higher stages of the aggregation of living matter than that of the 

 physiological molecule on which I have endeavoured to fix the discus- 

 sion. The question seems to me to be simply whether it is admissible 

 to regard that as capable of being brought to an absolutely static 

 condition. 



Conceive two such molecules, one known to be living, but static, 

 and the other dead, and both to be maintained in a condition in which 

 * Sachs, ' Text-book,' 2nd ed., p. 729. 



