DIFFUSION AND OSMOSIS 



59 



the current of water carries with it the blood globules which 

 produce the redness. 



The phenomenon of agglutination may also possibly be 

 due to osmotic pressure, a positive centre of diffusion attract- 

 ing and agglomerating the particles held in suspension. 



Tactism and Tropism. — The phenomena of tactism and 

 tropism may also be partly explained by the action of these 

 diffusion currents of particles in suspension, these polar 

 attractions and repulsions. 

 In all experiments on this 

 subject we should take 

 into account the possible 

 influence of osmotic pres- 

 sure, since many of the 

 causes of tactism or 

 tropism also modify the 

 osmotic pressure at the 

 point of action, and it is 

 possible that this modifi- 

 cation is the true cause of 

 the phenomenon. Osmo- 

 tactism and osmotropism 

 have not as yet been suffi- 

 ciently studied. 



Thus it may be said 

 that osmotic pressure 

 dominates all the kinetic 

 and dynamic phenomena 



of life, all those at least which are not purely mechanical, 

 like the movements of respiration and circulation. The study 

 of these vital phenomena is greatly facilitated by the concep- 

 tion of the field of diffusion and poles of diffusion, and of 

 the lines of force, which are the trajectories of the molecules 

 of the solutes, and the particles and globules in suspension. 



The Morphogenic Effects of Diffusion. — Many interesting 

 experiments may be made showing variations of the lines 

 of force in a field of diffusion, and how liquids subjected only 

 to differences of osmotic pressure diffuse and mix with one 



Fig. 5. — Liquid figures of diffusion. 

 The six negative poles of diffusion are 

 coloured with Indian ink. The positive 

 pole in the centre is uncoloured and is 

 formed by a drop of KN0 3 solution. 



