PHYSIOLOGICAL 403 



occurs in a horse or a man. One has dreams of perfect diagnoses of 

 species which will begin with a formula of the particular kind of 

 protein and end with an appreciation of the creature's psychical 

 mood, if it has got the length of having one. 



But to return to elementary chemistry, the particles of protein 

 and other organic compounds are present in multitudes in the 

 liquid medium, and there may be crowds of immiscible droplets 

 as well; and all this multitudinousness of minutiae means a very 

 large development of surface in proportion to the total mass. This 

 allows of a great intensity of changes, because the area of surface 

 is so enormous. Thus there is usually an electric charge on the 

 contact surface between any two phases, e.g. a complex solid 

 particle and a complex liquid medium; and the multitudinousness 

 of the sometimes quivering particles — quivering because bom- 

 barded by the restless molecules of the fluid — means a large surface 

 and therefore a more copious spring of electrification. It seems that 

 many of the marvellous properties of living matter, such as rapidity 

 of chemical change, are wrapped up with this colloidal state, which 

 means that multitudinous particles and droplets are suspended in a 

 complex medium. 



In the laboratory of a cell there is often a production of chemical 

 substances that cannot be regarded as being very intimately con- 

 nected with the living matter itself. Thus a cell may make granules 

 of a black pigment (melanin) or crystal-like spangles of guanin, 

 and all such things must be regarded as side issues, away from the 

 essential metabohsm. Now, if we could subtract from the total of 

 the cell-substance all these by-products, there would be left the 

 genuine living matter. In technical language, cytoplasm minus 

 metaplasm equals protoplasm. This is theoretically clear, but practi- 

 cally impossible. The probability is that there is no one substance 

 which should be called protoplasm, but rather a co-ordination of 

 proteins, carbohydrates, fats, and other stuffs which work into 

 one another's hands in a very effective way. There is much to be 

 said for using the metaphor of a firm; the partners are effective in 

 themselves, but the characteristic efficiency is due to their corre- 

 lation. But while a common purpose is the bond that keeps the 

 firm together, acting as a successful unity, we do not know what 

 the bond of union is in a cell. The persistent self-preservative 

 activity of protoplasm is much more difficult to understand than 

 the suicidal explosion of the gunpowder. In the protoplasm there is 

 for a time a succession of up-building, constructive, or anabolic 

 processes. But the clock that is thus wound up is ready to run down ; 

 and thus there is a succession of disruptive, destructive, or kata- 

 bolic processes. These two sets of processes, winding-up and running- 

 down, make up the metabolism of protoplasm; and it is charac- 

 teristic of life that the see-saw can be kept up for days or years or 



