37 



the chloropliyll bodies are built up. Such organized cal- 

 cium compounds would have a well-defined capacity for imbibition, 

 which would change with the replacement of the calcium by another 

 metallic element, and this altered water content must lead to a dis- 

 turbance in the structure, which must prove fatal if not remedied 

 in its initial stages. A peculiarity of protoplasm is that alteration of 

 the structure is soon followed by the chemical change from tbe active 

 to the i:)assive modification of its proteids. N'ow, when potassium oxa- 

 late acts on the inferred calcium protein compounds they yield in addition 

 to calcium oxalate the corresponding potassium protein com^^ounds, 

 which, on account of the different capacity for imbibition, can not physio- 

 logically replace the calcium compound. Moreover, neither tartr te 

 nor sulphate (which act much less energetically than the oxalate on 

 calcium compounds^) attack the nucleus or the chlorophyll bodies. 

 This also shows plainly that it is impossible to accept the view that 

 potassium oxalate becomes dissociated in the cells and that it is the 

 free oxalic acid which, on account of its acidity, kills the nucleus, since 

 potassium nitrate would be expected to act in just the same way.^ 



It will of course be difficult to prove microcbemically the formation of 

 calcium oxalate in the chlorophyll body or nucleus when x^otassium 

 oxalate is left to act upon them, since the amount of calcium in them is 

 naturally very small, judging from the great molecular weight of the 

 organized proteids with which it would be combined. Moreover the 

 formation of distinct crystals of calcium oxalate would be im^jeded by 

 the peculiar consistency of the living structures. It was claimed that 

 in view of the highly complicated conditions in the cells the assump- 

 tion of a direct connection between a working cause and an observed 

 pathological result could not be admitted, as the latter might be sim- 

 ply the effect of primarily produced " disturbances of nutrition." 

 However, this claim can not be sustained in the case of the action of 

 neutral oxalates upon the nuclei, for in the first place this proceeds 

 very rapidly in concentrations of over 1 per cent, and in the second 

 place the i)rocesses of metabolism in objects like Spirogyra proceed 

 very slowly. 



Further observations by Migula^ deserve to be mentioned here, as 

 they demonstrate that free oxalic acid is among the most poisonous of 

 organic acids. For example, in a solution of 0.004 per cent of free 



1 Calcium tartrate dissolves in about 2,000 parts of water. 



2 When acting on Spirogi/ra the potassium oxalate seems to pass direct to the 

 nucleus through the plasma strings and not through the tonoplast, but on the other 

 hand when potassium oxalate is contained in the cell sap of certain plants it 

 seems to be confined there by the density of the tonoplast, which also prevents its 

 direct contact with the nucleus in this case. In this connection Migula observed 

 some interesting facts with Spirogyra kept in well water to which very small quan- 

 tities of organic acids had been added. These were gradually oxidized iu the cells 

 into oxalic acid of which some was retained as neutral oxalate in the cell sap, 

 and yielded a precipitate of calcium oxalate when placed in a diluted solution of 

 lime salts. 



3 The Influence of Dilute Acids on Algai (Breslau, 1888). 



