62 THE MECHANISM OF LIFE 



precise architecture of a vast number of living organisms and 

 tissues, which are formed by the union of microscopic polyhedra 

 or cells. A section of such a polyhedral structure would 

 appear as a tissue of polygons. It is interesting to note that 

 the simple process of diffusion will produce such structures 

 under conditions closely allied to those which govern the 

 development of the tissues of a living organism. 



We may obtain this cellular structure by a simple ex- 



FlG. 8.— Pattern produced in gelatine by the diffusion of drops ol a solution 

 of nitrate of silver and of citrate of potassium. 



periment. On a glass plate we spread a 5 per cent, solution 

 of pure gelatine, and when set sow on it a number of drops of 

 a 5 to 10 per cent, solution of ferrocyanide of potassium. The 

 drops must be placed at regular intervals of 5 mm. all over 

 the plate. When these have been allowed to diffuse and the 

 gelatine has dried, we obtain a preparation which exactly 

 resembles the section of a vegetable cellular tissue (Fig. !)). 

 The drops have by mutual pressure formed polygons, which 

 appear in section as cells, with a membranous envelope, a 



