WATER 



concerns watery solutions it may give not only information 

 concerning the physical properties of particles which lie 

 within a certain range of size but additional knowledge of 

 the chemical action of water in a system of colloid particles. 

 The study of watery solutions is especially valuable inas- 

 much as protoplasm is such a solution. 



Water also is a functional component in the vital reac- 

 tions which take place in the cell. It plays a leading role 

 in the utilization of food materials: when these are broken 

 up into simpler compounds by the process of hydrolytic 

 cleavage water is taken up; when in turn these hydrolyzed 

 cleavage products are synthesized, water is lost. Whether 

 in a cell this cleavage or synthesis will occur, depends upon 

 the presence of water. Thus the movement of water from 

 place to place in a cell hangs together with the direction in 

 which the reactions run. Cellular oxidations demand the 

 presence of water. Water is an end-product of all energy 

 changes. Both conduction and contraction in cells depend 

 upon water. In the removal of secretory products and in 

 the elimination of excretory, water is necessary. 



Water thus is both part of the protoplasmic structure 

 and a functional component in vital manifestations. In 

 other words, it is bound up with the two fundamental 

 problems of cell biology, protoplasmic structure and func- 

 tion. The rhythm of water loss and water gain which every 

 cell exhibits during its history, serves by these fluctuations, 

 by its transitory nature, to emphasize the significance of 

 water — to offer us, as it were, a key to the puzzle of the 

 oscillatory changes which characterize life. Although dur- 

 ing its development the animal egg progressively loses water 

 — a dehydration imposed upon the rhythmical water-loss 

 and gain — it by no means ever reaches the stage of complete 

 dehydration. Its changing water-content therefore indi- 

 cates to us a possible approach to the problems, how water 



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