76 BIOLOGICAL CHEMISTRY 



material ; it probably forms a higher percentage of the weight 

 than this. If the solids do form a larger proportion than ten 

 per cent, the contrast between the amounts of the various 

 constituents would be more pronounced. 



Comparison of Inorganic Constituents of Aster ionella and its 

 Surroundings. 



Asterionella assuming Composition of 

 that 90% of the or- Brooklyn water, 

 ganism is formed of 

 water. 



per cent. per cent. 



Organic matter 4-248 



Silica (SiO 2 ) 4'948 . 0-001516 



Iron Oxide (Fe 2 O 3 ) 0*232 . 0-000034 



Lime (CaO) 0*145 0-004770 



Magnesia (MgO) 0-126 . 0-002432 



Potash (K 2 O) 0-122 . 0-000184 



Soda (Na 2 O) . 0-001390 



Manganese Oxide (Mn 2 O 3 ) 0-084 



Phosphate 0-067 



Sulphate 0-038 . 0-000184 



It is interesting that sodium is not mentioned in the analysis 

 of the plant, yet it is more abundant than potassium in the 

 water. 



The chemical differences shown in the above tables are 

 characteristic. They are seen to be differences in organic 

 and in inorganic material. 



In respect to the organic material the red blood cells are 

 surrounded by a solution containing protein but the plant 

 cells are surrounded by a solution without protein. 



The difference in organic compounds between the cells and 

 their surroundings is easily explained. The organic constitu- 

 ents of cells are mainly colloidal or insoluble substances such 

 as proteins, carbohydrates and lipoids, the diffusion of which 

 is easily limited. These substances can be hydrolysed to 

 simple diffusible substances such as amino acids, hexoses and 

 soaps, so that the cells can obtain their supplies by diffusion. 

 The simple substances are converted into more complex com- 

 pounds, thus the accumulation of organic material is possible. 



The difference in composition of inorganic materials is less 

 easily explicable. The inorganic ions cannot be decomposed 

 into simpler substances, so that one must discuss the way in 

 which these differences can be produced. Some substances 

 such as sulphur and phosphorus may exist partly as organic 

 compounds which form inorganic ions (sulphates and phos- 

 phates) on oxidation in the cells, but we cannot claim the same 

 form^of Bunion for such ions as those of potassium. 



