INDIVIDUAL LIFE OF THE CELL 183 



molecules and so to grow, and the whole organism exists 

 only through the reciprocal action of the single elementary 

 parts. ... In this eventuality it is the elementary parts 

 that form the active element in nutrition, and the totality 

 of the organism xan be indeed a condition, but on this 

 view it cannot be a cause" (p. 227). 



To help in the decision of this question, appeal must be 

 made to the facts established as to the cellular nature of the 

 organism and of its reproductive elements. We know that 

 every organism is composed of cells, which are formed and 

 grow according to the same laws wherever they are found, 

 whose formation therefore is everywhere due to the same 

 forces. If we find that certain of these cells all of which 

 we know to be essentially identical one with another 

 have the power when separated from the others of growing 

 and developing into new organisms, we can infer that not 

 only such cells but also all other cells have this assimilatory 

 power. The ova of animals, the spores of plants, the isolated 

 cells of lower organisms in general, all show the power of 

 separate assimilation and development. " We must therefore, 

 in general, ascribe to the cell an individual life, that is to say, 

 the combination of the molecules in the single cell does 

 suffice to produce the force whereby the cell is enabled 

 to draw to itself new molecules. The ground of nutrition 

 and growth lies not in the organism as a whole, but in the 

 separate elementary parts, the cells. The fact that it is not 

 every cell that can continue to grow when separated from 

 the organism is not in itself an objection to this theory, any 

 more than it is an objection to the individual life of a bee 

 that it cannot continue to exist apart from the swarm. The 

 activation of the forces existing within the cell depends on 

 conditions which the cell encounters only in connection with 

 the whole" (pp. 228-9). 



Schwann's next step is to discover what are the essential 

 forces active in the cell, and here he enters the realm of 

 hypothesis. He finds they can be reduced to two an 

 attractive force and a metabolic force. The attractive force 

 is seen in the process of cell-formation, where first of all the 

 nucleolus is formed by a concentration and precipitation of 

 substances found free in the cytoblastem, and in the same 



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