GROWTH 263 



two different, but homologous processes might be accomphshed by 

 the same part of the cell mechanism. Thus we could get a con- 

 ception of the number of different catalysts needed for the growth 

 process. 



Remembering the enormous surface of bacteria, it 

 seems surprising that intermediate construction products 

 have never been observed with bacteria, yeasts, or molds. 

 The construction of cell matter from building material 

 appears to be a continuous process comparable to the 

 moving belt method of automobile manufacture. The 

 molecules singled out for building stones have no chance 

 to escape or to get side-tracked. Once a certain CO2 

 molecule has been drawn by a nitrate bacterium into 

 the growth machinery, it cannot leave the cell; it is 

 destined to become a part of cell wall or protoplasm. 



This is perhaps the most remarkable part of the entire 

 growth process. The absence of partly synthetized 

 compounds in bacterial cultures makes us believe that 

 in one continuous process, the molecules are changed 

 at least to a state where they do not diffuse through the 

 cell wall. 



This would require a very definite arrangement of the 

 molecules in the cell. There are the molecules of the 

 energy producing zymase, present in quite large numbers. 

 These enzyme molecules are probably not scattered 

 around by chance, but are located at some definite parts 

 of the cell, or at least in definite position relative to the 

 synthetic catalysts. The molecules of these catalysts 

 are not all of the same type; there are different kinds 

 for different synthetic processes. These catalysts must 

 be arranged in some definite order so that the molecule 

 under construction can be ''passed on." Cytologists 

 have found from experiments on inheritance that each 

 gene has a definite location in its chromosome. All of 



