5 8 THE MECHANISM OF LIFE 



Consider, on the other hand, a centre of catabolism, where 

 the molecules are being broken up into fragments or smaller 

 oroups. The concentration of the solution is increased, the 

 osmotic pressure is raised, and we have a hypertonic centre of 

 diffusion. Every centre of catabolism is therefore a positive 

 pole of diffusion. Similar considerations as to the formation 

 and breaking up of the molecules in anabolism and catabolism 

 apply to polymerization. 



The diffusion field has similar properties to the magnetic 

 and the electric field. Thus there is repulsion between poles of 

 similar sign, and attraction between poles of different signs. 

 A simple experiment will show this. A field of diffusion is 

 made by pouring on a horizontal glass plate a 10 per cent, 

 solution of gelatine to which 5 per cent, of salt has been 

 added. The gelatine being set, we place side by side on its 

 surface two drops, one of water, and one of a salt solution of 

 greater concentration than 5 per cent. We have thus two 

 poles of diffusion of contrary signs, a hypotonic pole at the 

 water drop, and a hypertonic pole at the salt drop. Diffusion 

 immediately begins to take place through the gelatine, the 

 drops become elongated, advance towards one another, touch, 

 and unite. If, on the contrary, the two neighbouring drops 

 are both more concentrated or both less concentrated than 

 the medium, they exhibit signs of repulsion as in Fig. 4. 



Diffusion not only sets up currents in the water and in 

 the solutes, but it also determines movements in any particles 

 that may be in suspension, such as blood corpuscles, particles 

 of Indian ink, and the like. These particles are drawn along 

 with the water stream which passes from the hypotonic centres 

 or regions toward those which are hypertonic. 



These considerations suggest a vast field of inquiry in 

 biology, pathology, and therapeutics. Inflammation, for 

 example, is characterized by tumefaction, turgescence of the 

 tissues, and redness. The essence of inflammation would ap- 

 pear to be destructive dis-assimilation with intense catabolism. 

 We have seen that a centre of catabolism is a hypertonic 

 focus of diffusion. Hence the osmotic pressure in an in- 

 flamed region is increased, turgescence is produced, and 



