The Organisation of Matter 



less permeable than a pig's bladder or vegetable 

 parchment; such are the so-called semi-per- 

 meable diaphragms, which let the water or the 

 dissolving liquid through but hold back entirely 

 the bodies in solution, even crystallisable ones 

 such as salt or sugar. The membranes of living 

 tissues, in their infinite variety, act like sieves 

 with various-sized holes and sort out auto- 

 matically the products necessary to life. The 

 albuminoids and analogous products, due to 

 chemical reactions occurring inside the tissues, 

 are in general retained by the relative imper- 

 meability of the tissues, whereas the waste 

 materials of life, which are frequently crystal- 

 lisable, such as urea, are eliminated, thanks to 

 their greater diff usability. Thus diffusion is 

 life, or at least one of its most essential elements. 

 M. Stephane Leduc, Professor at the School 

 of Medicine of Nantes, has demonstrated this 

 important function of diffusion by some re- 

 markably clear experiments. What is necessary 

 to constitute an inorganic tissue analogous to 

 organic tissues? Simply to add, drop by drop, 

 salt water dyed with Indian ink to some pure 

 water spread in a thin layer in a flat-bottomed 



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