THE PHENOMENA OF LIFE 151 



corresponding weight. Thus growth, which has hitherto been 

 considered an essential phenomenon of life, is also a phenomenon 

 common to all osmotic productions. 



Osmotic growths like living things may be said to have an 

 evolutionary existence, the analogy holding good down to the 

 smallest detail. In their early youth, at the beginning of 

 life, the phenomena of exchange, of growth, and of organiza- 

 tion are very intense. As they grow older, these exchanges 

 gradually slow down, and growth is arrested. With age the 

 exchanges still continue, but more slowly, and these then 

 gradually tail and are finally completely arrested. The 

 osmotic growth is dead, and little by little it decays, losing its 

 structure and its form. 



The membranes of an osmotic growth thicken with aire. 



L> fS ' 



and thus oppose to the osmotic exchanges a steadily increasing 

 resistance. Young osmotic cells appear swollen and turgescent, 

 whereas old ones become flaccid, relaxed, and wrinkled. Ana- 

 logous phenomena are met with in living organisms, the 

 calcareous infiltration of the vessels representing the thicken- 

 ing and hardening of the osmotic membranes. The plumpness 

 of a child and the turgescence of young cells are but the 

 expression of high osmotic tension, while relaxation and 

 flaccidity of the tissues in old age betrays the fall of osmotic 

 pressure in the intracellular tissues. 



Circulation of the nutrient fluid may also be observed in 

 an osmotic growth as in a living organism. If we take a 

 calcareous growth with long ramified stems and dilute the 

 mother liquor considerably, we may see currents of liquid 

 issuing from the summit of the growth — currents which are 

 made visible by the cloudy precipitates which they cause. 

 The same current is also rendered visible in the stems them- 

 selves by the motion of the granulations and gas bubbles in 

 the interior of the osmotic cells. It is plain that some 

 such circulation must exist, for how could a membrane be 

 formed 150 centimetres from the seed if the membranoeenous 

 substance did not circulate through the stem ? A moment's 

 consideration will show that the propulsion is due to osmotic 

 pressure and not to mere differences of density, for the liquid 



