6o6 
Notes. 
physiological molecule is that it possesses the power of breaking up 
chemical combinations and reuniting their constituents in a way which 
absolutely eludes the methods available to the chemist, and entirely 
outstrides the pace at which he can preceed. There is the same 
kind of difference between the two methods as there is between 
arithmetic and the calculus in the solution of a mathematical problem. 
The question then is, how far the effects of Professor Dewar’s 
experiments, and of those who have preceded him in the same field, 
require us to modify our conception of the physiological molecule. 
Are we obliged to admit with Professor C. de Candolle and Messrs. 
Brown and Escombe that it may descend to a purely static condition ? 
This is really bound up with another question. The kinetic 
condition 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. Romanes showed 
that neither a high vacuum nor subsequent 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 germinative 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 o°C . 1 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 c slowed down ’ indefinitely. In such a case as now 
1 Sachs, Textbook, second ed., p. 729. 
