192 SCIENCE PROGRESS 



the effect persisted for 282 generations. Now, in this case the 

 restoration and maintenance of the " vital potential," as Calkin 

 calls it, cannot be due to the presence in the individuals of a 

 trace of the salt, for each generation would halve the amount, 

 so that as early as the twentieth generation less than a 

 millionth part would be left for each individual. One is 

 therefore driven to believe that the salt acts by restoring a 

 state which, in the absence of natural or artificial rejuvenescence, 

 wears out in about 170 generations. 



The continual flux of energy and of matter which seems to 

 be necessary to the maintenance of life implies a high degree of 

 molecular mobility. It is possible that living matter, like all 

 other forms of matter, tends to come into equilibrium with its 

 surroundings, and to attain a condition of too great stability. 

 To restore it the living substance needs stimulating at intervals, 

 just as a coherer needs tapping after each electric wave has 

 passed, in order to restore its particles to the non-conducting 

 position. These are vague possibilities, but physical science 

 furnishes a case so suggestively akin to artificial rejuvenescence 

 as to merit description. 



Matter is composed of molecules which in the liquid or solid 

 state are attracted to one another by forces of prodigious power. 

 Each molecule in the interior of a mass is pulled on the average 

 equally in all directions. But consider the surface layer, a film 

 only a few molecules deep. There the intermolecular forces are 

 necessarily to a great extent unbalanced, with the result that this 

 surface film acts something like a stretched elastic skin — it tries 

 always to compress the mass to the smallest possible dimension. 

 This, however, is not the only feature of the surface layer. It is 

 also the layer which is in contact with adjacent masses of matter, 

 gas, liquid, or solid, as the case may be. 



Now, masses of matter which do not mix when in contact, 

 and which therefore are defined by a surface of separation, are 

 rarely, perhaps never, without influence upon one another. 

 Interaction of the surface layer takes place, so that the balance 

 of molecular forces is modified, incomplete chemical reactions 

 occur, and a condition of molecular stress is produced which, 

 amongst other things, is manifested by the development of 

 electrical charges. 



These molecular events on surfaces are very potent ; they 

 can produce effects which are impossible and even inconceivable 



