308 THE EQUILIBRIUM OF COLLOID AND 



If it be remembered that a certain number of the amino-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 is 

 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 combinations is seen when dehydrated salts are dissolved in water, 

 for this process always causes heat development although the crystallised 

 salts after the residual combination is once completed always cause cooling 

 when dissolved on account of energy going latent as osmotic energy from 

 development of pressure* in the given volume of water. Similar heat effects 

 are seen in dissolving alcohol in water, and in the solution of free acids and 

 caustic alkalies in water. Other examples are the union of anaesthetics such 

 as chloroform with proteins, where the chloroform or other anaesthetic is in 

 all cases a chemically saturated body, yet the proofs of union with protein 

 are indisputable, there being finally obtained with sufficient pressure of chloro- 

 form actual precipitation, the precipitate containing chloroform in high 

 percentage. 



Pressure signifies in this chapter osmotic pressure. 



