No. 606] 



BIOLOGICAL ENIGMAS 



331 



However, such fusion can not fail to have an influ- 

 ence upon both the form and the strength of the fields in 

 question, since it involves a redistribution of the atomic 

 forces. This will take the form of an opening out, or ex- 

 pansion, which will necessarily reduce the coherence of 

 the group of atoms originally forming the individual 

 molecule. The degree of this ''opening" of the field 

 which occurs in crystallization must vary with the nature 

 of the molecule, and is probably smaller for organic sub- 

 stances than it is for the majority of inorganic com- 

 pounds. 



The mechanism of the autocatalytic process of crys- 

 tallization may be described somewhat as follows: 



In a solution, or a gas, the molecules of the dissolved 

 substance move about at random among the molecules of 

 the solvent, and the orientation of the axes of their fields 

 is entirely haphazard. However, as soon as a crystal of 

 the solute is introduced, the field forces of the surface 

 layer of atoms attract the dissolved molecules and at the 

 same time tend to turn them on their axes so that, as they 

 condense, they will fall into the pattern of the "space lat- 

 tice" upon the plan of which the crystal is built.^^ As 

 this is the most stable position which they can assume, 

 they will tend to remain there and form a new surface 

 layer of the crystal, to act in turn upon further molecules 

 in the solution, until all of the surplus dissolved substance 

 has been deposited. 



The primary force bringing the molecules to the crystal 

 face is of course not the surface field of attraction- 

 surface tension field— but their temperature motion— or 

 osmotic pressure. A similar force, of lower magnitude 

 in the case of a supersaturated solution, is constantly 

 disengaging molecules from the crystal and throwing 

 them back into the solution. The action apparently 

 ceases when the number of molecules deposited upon the 

 crystal snrfncc in unit tiiiU" boe.^nies rtMluccd owing to 

 deciva>itm- .•cih-ciitratinii to an OMiialitv Avitli the iinm- 

 ber ifavin- in tlio .^anie intei-val. 



