12 BIOTIC STKUCTUKE AND BIOTIC ENERGY 



root of the varying activities of the cells, and of all physiological 

 and pathological changes. 



We may now pass briefly in review some important instances 

 of these slower variations in colloidal condition which give rise to 

 phasic or intermittent discharges of energy as outlined above. 



In the first instance, it may be pointed out that these changes 

 in character of colloidal solution requiring considerable intervals 

 of time for their evolution are not confined to colloids forming part 

 of living cells, although there they reach their acme of complication 

 combined with delicacy of balance and a perfect cosmos of co- 

 ordination. For Graham has shown that the possession of energy 

 and slow change are characteristic of inorganic colloids, and 

 recently Moore and Roaf have shown that organic colloids such as 

 gelatine solutions possess a kind of hysteresis, as a result of which 

 they only respond slowly to changes in external energy con- 

 ditions, so that a change may go on for days before coming to rest. 



For example, heating a 10 per cent, solution of gelatine up to 

 70 to 80 C. for a short time causes a partial splitting up of the 

 solution aggregates, accompanied by a considerable rise in osmotic 

 pressure, as directly recorded in the osmometer. If, now, the solu- 

 tion be allowed to cool to a little above its gealing-point, say to 

 40C., then, instead of the osmometric pressure dropping back in an 

 hour or two, as it would from a mere temperature change by means 

 of compensating diffusion of water, it is found experimentally that 

 the pressure requires two or three days to drop to its original value, 

 but does finally attain this with lapse of time, after which the above 

 cycle may be repeated. 1 



This type of phenomenon, varying in quantitative amount with 

 the type of colloid or of living protoplasm affected, appears to give 

 an indication for explaining the phasic activity found with varying 

 speeds in different types of cell, and giving rise to their peculiar 

 periods of charging and discharging, of activity and rest, of fatigue 

 and recuperation. 



If we take once more the heart-beat as our example, we observe 

 immediately after each beat the refractory period, followed by a 

 period of colloidal rearrangement, in which the irritability or ten- 

 dency to reversed change gradually heaps up to a point at which the 



1 The author just now has discovered a similar rhythm, or hysteresis, in 

 the blood proteins, but in a reversed direction. Heated serum agglutinates, 

 as shown by fall in osmotic pressure, and then in a few hours reverses. 



