1893. EXPERIMENTS ON LIVING CELLS. 433 
laboratory in a brass tap. The first litres drawn were strongly oligo- 
dynamic, from contact with the lead and with the copper of the tap ; 
after some quantity had been run off, the water was neutral. The 
distilled water was rendered hurtful by the apparatus used. Neutral 
water could be obtained at any time by distilling in glass alone. 
Nageli’s papers on oligodynamics were handed to Professor 
Cramer of Ziirich in the spring of 1892, who at once instituted a care- 
ful examination of the recorded experiments, with the result that this 
peculiar power of weak metallic solutions was completely verified. 
He followed very much on the lines of the previous research, testing 
the effect on Spivogyva cells of copper, copper sulphate, mercury, 
mercuric chloride, and Dr. Léw’s solution of alkaline silver nitrate, 
and the results, with slight variations, corresponded to those already 
determined by Nageh. 
The water used in Ziirich comes from the lake, is exceptionally 
pure, and is conveyed tothe town in iron pipes. With the exception 
of the first litre drawn, which had been in contact with the brass tap 
of the laboratory, it was, in Nageli’s sense, absolutely neutral. The 
distilled water usually employed was prepared in a copper vessel 
lined with tin. It reacted variously, and especially seemed to lose 
oligodynamic power if it had been in several vessels, or if it had 
stood some time after preparation. In this connection, we may also 
note that he found the oligodynamic reaction was in proportion to the 
size of the vessel used in experiments. If there was much of the 
metallic solution in a small vessel, the effect on the cells was rapid ; 
the same solution acted much more slowly when a drop of it was 
used on a glass slide where the glass surface exposed was so much 
greater in proportion to the quantity of metallic molecules present. 
The solution became weaker the longer it was allowed to stand, and 
repeated boiling or filtering neutralised it altogether. Water dis- 
tilled in glass was, he also found, invariably neutral. 
Professor Cramer chose, for the purpose of research, three species 
of Spivogyra; one of these, Sp. guinina, is of a delicate texture with 
only one spiral chlorophyll band, the other two, Sp. densa and Sp. 
setiformis, are coarser. The reaction depended, to a certain extent, 
on the species; Sf. setiformis, with closely-wound spirals, always 
resisted the action of the metal longer than the other two species. 
The sensitiveness of the plant was, however, intensified if it had 
been long under cultivation in the warm temperature of the labora- 
tory, in which case the cells lengthened, and the spirals were, in 
consequence, looser and more sparse. He used for his control 
cultures large glass vessels filled with ordinary Ziirich water. 
Oligodynamic reaction was most easily obtained by water in 
which copper had remained from one to three days. If a healthy 
plant growing in neutral water were strewn with copper turnings, 
the chlorophyll bands very quickly shrunk from the sides of the cells 
in contact with the copper. A glass slide that had been in contact 
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