426 TRANSACTIONS OF THE CANADIAN INSTITUTE. [Vo.. VIII. 
would proceed at —220° C., that is, the temperature of interstellar space, 
at one thousand millionth of the rate which obtains at 10° C., so that a 
journey of 3.000,000,000 years in space would be no more injurious in 
effect than one day’s exposure to a spring temperature and sunlight on 
this planet. Inside of the solar system the temperature would be some- 
what higher owing to the proximity of the sun, but the journey would 
be short and the microorganisms would survive. 
The low temperature of interstellar space would reduce to a 
negligible minimum both photo-chemical changes and the rapidity of 
desiccation in the microorganisms on their journey. Schroeder has 
shown that Pleurococcus which grows on moist surfaces, as, for example, 
the bark of trees, and Scenedesmus whose normal medium is water, may 
be kept alive for twenty and sixteen weeks respectively, in a desiccator 
over concentrated sulphuric acid. Further, it is natural to suppose that 
desiccation, that is, evaporation, would be proportional to the vapour 
tension of water, which at —220° C., has not been directly measured, but 
can be computed approximately from the latent heat of evaporation by 
means of a formula given by van’t Hoff and from it Arrhenius concludes 
that desiccation does not progress any farther in millions of years at 
—220° C., than in one day at 10° C. above zero. 
The low temperature of interstellar space, therefore, reduces enorm- 
ously in living matter the chemical changes that diminish vitality, the 
rapidity of photo-chemical changes and of desiccation and, in conse- 
quence, the life of microorganisms traversing interstellar space would 
be prolonged sufficiently to enable them to reach the earth and the 
other planets of the solar system in a condition to continue life and 
reproduce themselves in their new environment. 
Arrhenius admits, however, that the organisms which thus arrive 
would in their first contact with the atmosphere of the earth encounter 
a temperature of notless than 100° C. due of course to that gener- 
ated by friction. This he holds will not necessarily sterilize the organ- 
isms as protein, which is their physical basis, is not in the very dry 
state coagulated by such a high temperature, but it is exceedingly 
doubtful indeed if organisms which are supposed to retain in their long 
journey through’ space moisture enough to enable them to begin terres- 
trial life, would be profoundly unaffected by a temperature which 
ordinarily is germicidal. 
There are in the main two objections to the Panspermic Theory, 
The first and chief is that it does not account in the last analysis for 
