THE INFLUENCE OF ENVIRONMENT 291 



and determining heredity, the eventual structure, as again the 

 specific functions of a cell, are determined by the sum of the 

 forces acting upon that cell ; structure and function are adapta- 

 tions to environment. It is not only the nutritive material 

 absorbed by the cell that determines the characters thereof, 

 but its position relative to other cells in the economy. From 

 the first the cell continues to proliferate until the sum of the 

 above-mentioned forces brings it sooner or later to a condition 

 of equilibrium, until the amount of nutrition absorbed (and the 

 resultant energy) is fully utilized in maintaining the cell in the 

 status quo. And when this point is reached, the products of 

 nuclear and cell metabolism, as they are formed, become used 

 up in the performance of function. There is no sufficient surplus 

 or redundancy of material to permit the cells to undergo simul- 

 taneously those material transformations which result in cell 

 division. Disturb the environment of the cell, remove certain 

 of the forces acting upon it so that the cell energy previously 

 devoted to counteracting the effects of those forces may now be 

 diverted into and employed in other directions, and then un- 

 employed energy may be utilized for growth, or perhaps, more 

 exactly, the material heaped up by constant assimilation, by 

 its very presence in the nucleus, stimulates this to undergo 

 mitotic changes. As a matter of fact, numerous examples can 

 be adduced of overgrowth of tissues due to removal of forces 

 normally acting upon these tissues, overgrowth which continues 

 until such time as the sum of the forces acting upon the newly 

 formed cells becomes equal to the utilization of the sum-total 

 of the cell energies ; then continued growth comes to an end. 



This, on the one hand, namely, that removal of forces acting 

 upon the cell from without leads to its passing from the functional 

 to the proliferative state ; or, if it be in the proliferative state, 

 leads to its continuing in the same ; on the other, increased 

 absorption and utilization of nutritive material affords the 

 opportunity for increased exhibition of energy, increased 

 katabolism. 



INERTIA OF CELLS 



Now increased absorption and assimilation is in general a 

 response to previous or concurrent increased katabolism and 

 increased activity. So long as this increased assimilation 



