GENERAL PHYSICAL CONSTITUTION' OF LIVING MATTER 41 



physiological action immediately after the discovery of this action. 

 At that time the various authors, e.g. von Biebra and Harless, ex- 

 plained the action of ether and chloroform on the assumption that these 

 substances caused the fat to leave the cells by dissolving it. This does 

 not seem to harmonize with the fact that a person so soon recovers from 

 the effects of a narcosis. Overton showed, moreover, that ciliary cells, 

 when narcotized in water by ether or chloroform, may resume their 

 activity when brought back into pure water. This would not be pos- 

 sible if the narcotic effect of ether or chloroform had been due to the 

 diffusing of fats from the cell; but the fact that a person can recover 

 from the action of narcotics does not prove that their action is a purely 

 physical one. A person who becomes unconscious from the lack of 

 oxygen may also recover, if oxygen is admitted again, soon enough, 

 and yet no one would conclude from this that the action of oxygen is 

 purely physical. The rapidity of the absorption of narcotics may be 

 due to their solubility in oil, and yet the effect they produce may be 

 due to something entirely different. 



5. OSMOTIC PRESSURE AND THE EXCHANGE OF LIQUIDS BETWEEN 

 THE CELLS AND THE SURROUNDING LIQUID 



The observations of Traube, Quincke, Ramsden, and Overton 

 have given us some hints as to the nature of the surface films which 

 surround protoplasm. Their importance lies in the fact that the con- 

 tents of the cells are chiefly liquid, and that an exchange of dissolved 

 substances occurs steadily between these substances and their sur- 

 roundings. Animal cells are surrounded by a liquid which resembles 

 sea water in its constitution, though its osmotic pressure is in land and 

 fresh-water animals, and in some marine animals, less than that of 

 sea water. The main force for the exchange of dissolved substances 

 between the cells and the surrounding solution is the osmotic pressure. 

 Inasmuch as the cells take up the salts, proteins, fats, and carbohy- 

 drates that are dissolved in the blood, we cannot accept Overton's 

 view that only water and those substances which are soluble in fat pass 

 through the membranes, and that salts generally cannot pass through. 

 We hold that the cell walls are not impermeable to salts, and that there 

 is only a difference in the rate of diffusion of the various substances, 

 many salts diffusing only very slowly into the protoplasm. The con- 

 sequence is that for short experiments the cells act as if they were im- 

 permeable for salts and permeable for water only. When cells are 

 put into salt or sugar solutions, whose osmotic pressure is higher than 

 that of the liquid of the cells, the cell loses water; and in the case of 



