6 



Water 



lI^^ater, quantitatively the most important com- 

 pound in the inanimate world, and the most ubiquitous, 

 holds the same place in the animate. Roughly, living cells 

 can be said to be made up of two-thirds of water. Water 

 is a structural part of every living protoplasmic system; life 

 does not exist without it. Even when in a highly dessicated 

 state, animals, such as rotifers and tardigrades, are not 

 completely anhydrous. 



Living protoplasm is an aqueous colloidal solution. In 

 view of the prevailing emphasis nowadays placed upon the 

 colloid state of protoplasm, it is astonishing how little we 

 know of the manner in which water forms a part of the 

 living state. Is protoplasm an emulsoid colloid t To what 

 extent is It a suspensoid colloid 1 Is it a structure in which 

 water encloses other substances or one In which the other 

 substances enclose water, or is It of both types t With 

 these questions I refer to the ultra-microscopic structure of 

 protoplasm — that is, of the ground-substance — for to this, 

 as already pointed out, the colloid-chemist by his own 

 definition of colloid-chemistry should address himself if 

 he wants to study living substance, and not to the micro- 

 scopically visible inclusions. The solution of many funda- 

 mental problems in biology is postponed because of our 

 Ignorance of protoplasmic structure. The colloid-chemist 

 could render great service to medicine and biology by dis- 

 sipating this ignorance. As I see It, the main significance 

 attached to the study of matter in that physical state called 

 the colloidal is that it deals with solutions; and where it 



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