CRYSTALLOID IN LIVING CELLS 9 



molecules, so that these tend to unite with the elimination of the 

 elements of water above mentioned. Now it is clear, since each 

 combining amido-acid had two free poles, that after this union has 

 occurred there will still be left, in the new combine of double the 

 molecular size, two opposite poles free ; and if this larger new mole- 

 cule is brought, under suitable conditions, in chemical Contact with 

 more molecules, that further additions of like nature can occur. 



If it be remembered that a certain number of the amido-acids 

 possess more than one basic group, or more than one acidic group, 

 it is further obvious that it is not necessary for this process of 

 growing to extend out in a single chain ; but that branching may 

 occur, and union of branches, so that a ramification or network can 

 be formed in all three dimensions of space. 



There is no limit but the stability of the whole chemical system 

 to this growth proceeding until a point is reached at which, with 

 the particular chemical agencies for union and condensation at 

 hand, there is an equilibrium between the forces building up or 

 synthesising and the forces tending to disrupt. 



In the same way by protein unions the substances of the pro- 

 toplasm or bioplasm can be formed, until new limiting conditions 

 again fix a maximum, and, it may be added, though the agencies 

 at work may differ in type, similarly the bioplasm can increase in 

 aggregation until a maximum cell volume has been reached for 

 a particular cell, and cell division becomes essential for further 

 multiplication. 



In this process of growth it will be observed that there must 

 be left at the end of the process a number of poles of opposite 

 type. These poles, although they are chemically saturated (for as 

 pointed out above the elimination of the elements of water are 

 required at each union), must still possess what has been termed 

 residual affinity, 1 and have sufficient power to attract a group of 

 opposite polarity and hold it very loosely attached. 



1 This residual chemical affinity is seen when compounds, saturated as regards 

 ordinary chemical values, combine with one another, such as neutral salts with 

 their molecules of water of crystallisation. The energy of such residual combina- 

 t i..iis is s. en when di-hydrated salts are dissolved in water, for this process always 

 causes heat development although the crystallised salts after the residual combina- 

 tion is once completed always cause cooling when dissolved on account of energy 

 going latent as osmotic energy from development of pressure l in the given volume 

 of water. Similar heat effects are seen in dissolving alcohol in water, and in the 



1 Pressure signifies in this article osmotic pressure. 



