ON ENZYMES AND LIVING CELLS 207 



of light under certain conditions in producing ophthalmia. Here 

 may be mentioned also the action of various other forms of radiant 

 energy upon living cells, such as the X rays and Finsen rays, and 

 the radiations of radium, which act as such powerful stimulants 

 upon living cells. 



Action of Acids and Alkalies and of Neutral Salts upon Enzymes 

 and Living Cells. In considering the value of foodstuffs such as 

 protein, carbohydrates, and fats as sources of energy to the body, 

 we are too apt to forget that energy is not the only thing required, 

 and that in order to use this energy, the integrity of the mechanism 

 for its conversion or transformation viz., the living cell is no less 

 important. For the preservation of this integrity, the simple 

 inorganic salts, and a due proportionality between acid and alkali, 

 are no less important, and such simple substances are no less indis- 

 pensable than the organic foodstuffs. It has been shown by 

 Ringer and others that normal physiological activity is not possible 

 in the presence of the organic or energy-yielding constituents alone, 

 that these may be present in abundance, and yet the tissue be 

 entirely incapable of functionating unless it is also fed with certain 

 inorganic constituents. Ringer further showed in the case of the 

 frog's heart that there must be a certain balance maintained 

 between the various inorganic constituents, that sodium chloride 

 alone could not maintain the activity, but that it was necessary 

 to have present both potassium and calcium in certain balanced 

 proportions. Working on the basis of his experiments, he devised 

 " Ringer's solution," containing these substances in the proper 

 concentrations for the preservation of physiological activity, which 

 has since, in various modifications, been employed by most subse- 

 quent workers on the subject. 



The work begun by Ringer has been continued by many workers, 

 and extended into observation of the effects of variation of the 

 inorganic salts, and of acids and alkalies, not only upon a mainten- 

 ance of physiological activity, which was the problem chiefly studied 

 by Ringer, but also of the effects upon rapidity of cell growth and 

 division and of reproduction. 



The physiological balance of salt solutions first discovered and 

 investigated by Ringer, in the case of the frog's heart, was later 

 extended by him to skeletal muscle and to marine organisms, and 

 shown by the same observer to be a general law. 



The valuable results obtained by many independent later 



