2i8 PHYSICAL BASIS OF CIVILIZATION 



stances and forces of the environment, and on the 

 other with the substances and forces of the stratum 

 immediately inside of it. Since the substances and 

 forces of the environment differ from those of 

 the outer stratum, therefore would the interactions, 

 necessarily following contact, tend to modify its 

 composition and molecular arrangement. Because 

 it is very probable, therefore let it be assumed that 

 the first modification produced in the outer stratum 

 made a cell wall of it. This transforms the histo- 

 blast into a cell. Since the efficiency of every force 

 diminishes in the square of the distance from its 

 source, since the cell wall, no matter how infini- 

 tesimally thin, is mathematically divisible into an 

 outer and an inner half, therefore, taking the 

 thickness of one of these halves as the unit, it 

 follows that where the cell wall is in contact with the 

 interior cell substance, the forces originating in 

 the environment can possess one-fourth of their 

 original efficiency only ; and applying the same line 

 of reasoning to the whole substance of the cell 

 with its infinite series of infinitesimally thin mathe- 

 matical strata, the inference is reached that the 

 changes producible by external influences are 

 infinitely small at the center of a cell, and infinitely 

 great by comparison at its surface. 



External influences in their transit to the center 

 pass through all intermediate strata. In their 

 passage they must, by interactions with the sub- 

 stances through which they pass, lose a portion of 



