The Organitm (tinl it* CKcuriitry 117 



different phases, though every change in any phase affects 

 the chemical and physico-chemical equilibrium of the whole 

 system. Among these phases arc to be reckoned not only 

 the differentiated parts of the bioplasm strictly defined (if 

 we can define it strictly) the macro- and micro-nuclei, nerve 

 fibers, muscle fibers, etc., but the material which supports 

 the cell structure, and what have been termed the meta- 

 plasmic constituents of the cell. These last comprise not 

 only the fat droplets, glycogen, starch grains, aleurone 

 grains, and the like, but other deposits not to be demon- 

 strated histologically. They must be held, too a point 

 which lias not been sufficiently insisted upon to comprise 

 the diverse substances of smaller molecular weight and 

 greater solubility, which are present in the more fluid phases 

 of the system, namely, the cell juices. It is important to re- 

 member that changes in any one of these constituent phases, 

 including the metaplastic phases, must affect the equilib- 

 rium of the whole cell system, and because of this necessary 

 equilibrium-relation it is difficult to say that any 

 one of the constituent phases, such as we find permanently 

 present in a living cell, even a metaplastic phase, is less 

 essential than any other to the 'life' of the cell, at least 

 when we view it from the point of view of metabolism." 



Or, again notice this: "For the dynamic chemical events 

 which happen within the cell, these colloid complexes yield 

 a special milieu, providing, as it were, special apparatus, and 

 an organized laboratory." 



Some of the particularly important features of the "col- 

 loid complexes" which make them a "special milieu," i.e., 

 a special environment, of so remarkable a character are: 

 The commingling in them of the solid and fluid, or "gel" 

 and "sol" conditions of the colloids ; the "surface effects" of 

 colloidal particles as the free surface energy, the osmotic 

 pressure, and perhaps the enzymic action, of such surfaces; 

 the so-called aihorptive properties of solid colloids, that is, 



