THE PHYSICAL BASIS OF LIFE 193 



in matter in bulk. It is, for instance, not only possible, but 

 probable, that in the surface layers the conditions may some- 

 times be such as to associate decrease of volume with decrease 

 of pressure, a relation so subversive of ordinary experience as to 

 be unthinkable. In the surface layer a gas may be condensed to 

 the liquid state when far above its critical temperature and below 

 its critical pressure. Chemical changes occur or are suspended 

 under conditions of temperature and pressure totally unlike 

 those controlling the same changes in masses of matter. Con- 

 centration, electric conductivity, all physical properties in fact, 

 become abnormal, therefore when the surface energy forms a 

 large fraction of the total molecular energy, as in films, or fluid in 

 fine capillaries, ordinary chemical or physical knowledge fails us. 



Now, there is no lack of evidence to prove that the lifelike 

 characteristics of colloidal matter, its capacity for storing 

 impressions, the elusiveness of its chemical and physical states, 

 are due to the fact that an exceptionally large fraction of its 

 energy is in the form of surface energy. 



There is also direct and unmistakable evidence in the nature 

 of the effect of various salts upon the heart-beat, and in the 

 optical characters of thin films, that living matter also contains 

 a very large proportion of surface energy per unit of mass, 

 and the curious and extreme physical and chemical powers 

 which it manifests are without doubt largely due to this cause. 

 Now, it is just in experiments on surface energy that one finds 

 a case analogous to the effect of the salt in bringing about 

 rejuvenescence of senile protoplasm, or in awaking the dormant 

 powers of an unfertilised egg. 



It has been shown recently by a French physicist, M. Perrin,, 1 

 that by the use of minute amounts of salts one can give to the 

 surface energy of a solid a certain direction — one can fix in the 

 surface layer certain qualities which, for instance, define the 

 electric properties of the surface. The effect once produced, 

 no amount of washing will undo it ; the salt can be removed, 

 the effect remains. So far as we know, in the absence of 

 active chemical intervention it will endure for all time, 

 always exerting a directive influence upon the molecular events 

 in its neighbourhood. In these experiments there is, it 

 seems to me, a real clue to the nature of the phenomena of 

 rejuvenescence. 



1 Journ. d. Chem. Physique, ii. p. 6i, and iii. p. 50. 



13 



