INORGANIC CELL-CONSTITUENTS. 



125 



Fluids. 



Water. 



Solids. 



The condition of semi-solidity of organic tissues, which we found to 

 be so essential to the carrying out of the physical processes in cell life, 

 is rendered possible by the amount of water and the condition in which 

 it is held by the different cells. A remarkable ' fact in connection with 

 the manner in which water is held by the animal organism is that there 

 are certain tissues and organs in which the percentage of water found is 

 in excess of the percentage of solids, without the organs assuming the 

 fluid form; indeed, again, there are certain semi-solid organs whose per- 

 centage of water is even greater than that of the animal fluids ; thus, the 

 kidneys contain a larger percentage of water even than the blood. This 

 shows therefore that the manner in which the water is held by such 

 tissues must be different from that in which it exists in the animal fluids, 

 where it occupies more or less the role of a medium of solution. The 

 consistence of many fluids in the animal body is not dependent so much 

 on the amount of water present as on the nature of the substances which 

 are in solution; thus, mucus has a considerably larger percentage of 

 water than blood, and yet is apparently a denser fluid. As already de- 

 scribed in the section on Physical Processes in Cells, the water of the 

 semi -solid organic bodies enters their elementary intermolecular spaces, 

 and it is a peculiarity of organized bodies that they may absorb a 

 quantity of water greatly in excess of their own weight without losing 

 their semi-solid condition. In such cases it is not water alone that is 

 absorbed, but water always containing different inorganic salts in solution. 



