26 PHYSIOLOGICAL ROLE OF MINERAL NUTRIENTS. 



beet and that of starch in the potato." Potassium and magnesium 

 chlorids also depress the starch content of the potato, probably on 

 account of an increased amount of water being- taken up. Potassium 

 sulphate, being less absorbed by the tubers, has no such action.-' 



Observations, not strictly relating - to chlorids alone, are the follow- 

 ing: A solution of 1.8 per cent sodium chlorid will prevent the germi- 

 nation of wheat (Coupin). Certain alga 1 , such as Spirogyra crassa, 

 will suffer in culture solutions containing 0.5 per cent potassium or 

 sodium chlorid, while lower kinds an 1 not affected by 1 per cent chlorid 

 of sodium, or even more, and certain bacteria and small yeasts may 

 grow even in the presence of from 10 to 12 per cent. 



ABSORPTION OF CHLORIDS BY AQUATIC PLANTS. 



The considerable absorptive power of many aquatic plants for chlorids 

 is interesting. The ash of Nym/phsea alba, amounting to 7 to 10 per cent 

 of the dry matter, was found to contain 1) to 23 per cent of chlorin 

 and that of Spirogyra nitida 24 per cent. The ash of such plants does 

 not always show a sufficient potassium content to bind all the chlorin 

 present; hence a part of the latter will in such cases lie present as 

 sodium chlorid. In order to estimate the absorptive power of Elodea 

 ainadf-nxix, the writer has determined the amount of chlorin in water 

 which ran slowly through a basin in which this plant was cultivated, 

 and found that the water contained, per liter, 4.5 mgr. chlorin. The 

 amount of ash in the plant was found to be 8.04 per cent, in which 

 was 0.0 part chlorin; hence the plant contained in the dry matter over 

 one thousand times as much chlorin as an equal weight of the water 

 in which it was grown. 



SODIUM CHLORID IN ANIMALS. 



Chlorin, in the form of sodium chlorid, plays an important role in 

 animals, the formation of normal gastric" juice, containing 0.2 percent 

 hydrochloric acid, being impossible in its absence. An idea of its 

 great importance for the blood may be inferred from the fact that on 

 an average about one-half of the blood ash consists of chlorid of sodium. 

 Nearly one-third of the ash of the white of hens 1 eggs is made up of it. 

 This salt can not be replaced by potassium chlorid, as the latter in the 

 same quantity would exert a noxious influence on the animal. It facil- 

 itates the absorption of protein in the animal organism and increases 

 metabolism. An adult human body contains about 200 grams of 

 sodium chlorid. 



FLUORIDS IN PHYSIOLOGICAL RELATIONS. 



The presence of calcium fluorid in teeth and bones was known long 

 ago. Moles [1856] observed nuorin compounds also in various other 



"The injury to the burning qualities of tobacco should also be mentioned. 

 ^Sjollema, Journ. f. Landwirtschaft. , vol. 47, p. 805. 



