318 PROPERTIES OF THE COLLOIDAL CONSTITUENTS 



magnesium. Furthermore both the cathartic and the anesthetic 

 actions of magnesium salts are antagonized and annulled by the 

 administration of calcium salts. At all events barium salts share with 

 the calcium precipitants the common property of inducing hyperirri- 

 tability in muscular tissues, while the exceptional sensitiveness of the 

 intestinal musculature to magnesium may be perhaps regarded as 

 affording another instance of the diverse susceptibility of the various 

 types of tissue-cells to the influence of changes in the inorganic environ- 

 ment. That the intestinal musculature is not the only tissue which 

 is profoundly affected by magnesium salts is shown by the fact that 

 the introduction of a considerable excess of magnesium chloride into 

 the blood-stream induces Glycosuria in rabbits. 



THE MUTUALLY ANTAGONISTIC ACTION OF SALTS, AND PHYSIO- 

 LOGICALLY BALANCED SOLUTIONS. 



We have already seen that a small proportion of calcium inhibits 

 the action of sodium salts in inducing rhythmic pulsations of many 

 contractile tissues. This is, however, merely a particular instance of a 

 very general phenomenon, as the investigations of Loeb in animal 

 physiology and of Osterhout in plant-physiology have most abundantly 

 demonstrated. 



For example, the fertilized eggs of the marine fish Fundulus will 

 develop normally in distilled water. Inorganic salts are therefore not 

 necessary for their nutrition. They will also develop normally, of 

 course, in sea-water in which the various saline constituents other than 

 bicarbonates and phosphates are present in approximately the following 

 concentration and proportion (Van t'Hoff's solution) : 



5/8m sodium chloride 1000 parts by volume 



5/8m magnesium chloride 78 " " 



5/8m magnesium sulphate 38 " " 



5/8m potassium chloride . . . . 22 " " 



5/8m calcium chloride t 10 " " 



In | m sodium chloride solution, without the admixture of the other 

 salts, however, the eggs will not live for more than twelve hours, 

 despite the fact that this solution is isotonic with sea-water. Evidently 

 sodium chloride is definitely toxic for these organisms. In the following 

 mixtures: 



96 c.c. of 5/8m NaCl + 4 c.c. of 5/8m MgCl 2 

 96 c.c. of 5/8m NaCl + 4 c.c. of S/Sm.KCl 

 96 c.c. of 5/8m NaCl + 4 c.c. of 5/8m CaCl 2 



they will live only for about twenty-four hours or even less. When the 

 eggs are placed in the following solutions: 



96 c. c. of 5/8m NaCl + 2 c.c. of 5/8m MgCh + 2 c.c. of 5/8m CaCl 2 

 96 c.c. of 5/8m NaCl + 2 c. c. of 5/8m MgCl 2 + 2 c.c. of 5/8m KC1 

 96 c.c. of 5/8m NaCl + 2 c.c. of 5/8m CaCl 2 + 2 c.c. of 5/8m KC1 



