June. 1893. EXPERIMENTS ON LIVING CELLS. 429 



nucleus into a round ball. To this latter result Nageli gave at first 

 the name Isa<^itdt, but later he changed it to Oligodynamic. 



As to the effect of solutions generally on Spirogvra a.r\d other cells, 

 Nageli enumerates three ways in which they may prove fatal — physi- 

 cally, by inducing plasmolysis, for instance; chemically, by poisoning 

 the plant ; and lastly, oligodynamically. The last-mentioned resulted 

 when the chemical solution was so diluted that the reaction could not 

 be one of simple poisoning, but must be due to some other influence. 



Nageli pursued the research still on the same lines ; he put the 

 filaments into Dr. Low's solution, diluted quadrillion-fold, till, finally, 

 he concluded that no calculable trace of the poisonous silver nitrate 

 was present ; the result was equally satisfactory from an oligodynamic 

 point of view, the cells died often in less than four minutes. He now 

 turned his attention to the water used in the solution, which was 

 distilled in the ordinary way, and the conclusion arrived at was a 

 startling one, namely, that pure water is a dangerous and hurtful 

 fluid. After boiling, the evil effects diminished, they did not quite 

 disappear. 



Another series of experiments was tried with mercuric chloride — 

 a still stronger poison. This was diluted down to septillion-fold, and 

 the plants died as before. Professor Cramer has calculated that in 

 order to dilute i milligramme of mercuric chloride to this extent, we 

 should require more water than there is on our planet. A globe of 

 water would be necessary thirteen m.illion geographical miles in diameter, 

 which would reach almost from the sun to Venus, and the molecules 

 in such a solution would be separated from each other by a distance 

 equal to two-thirds of the earth's diameter. He concluded, as we 

 do, that the solution would be harmless, so far as mercuric chloride 

 was concerned. This experiment proved conclusively that the evil 

 was due to something other than chemical poison. 



Attention was next turned to the glass vessels used, to see if the 

 effect was produced by mechanical action. The glasses were tested 

 in various ways, by movement, by covering them, etc., but no diffe- 

 rence was visible in the behaviour of the solution ; the Spirogyra died, 

 and yet not always; in four out of this series of experiments the 

 Spirogyra remained uninjured in the diluted solution. Again, boiling 

 was tried, and in most cases the water was restored — we can hardly 

 say to purity, but to harmlessness, or, as Nageli terms it, it was 

 rendered neutral. 



Meanwhile, control experiments with pure distilled water had 

 been carried on quite successfully in glasses full of Spirogyra. A 

 culture was now tried with the same water and only a few filaments ; 

 as Nageli expected, they died, if anything, still more quickly than in 

 the diluted chemical solution, and water from the tap acted frequently 

 exactly like distilled water. 



A further research was now entered on to test the water, and as 

 distilled water was, on the whole, more fatal than tap-water, he 



