Some years after the death of Nageli (i), in I89I, there was published by Schwendener, a paper which had been found among Nageli's manuscripts, entitled ' Ueber oligodynamische erscheinungen in lebenden Zellen.' In this paper Nageli demonstrated the extreme sensitiveness of certain living plants to very minute traces of various metals. BIOCHEMICAL JOURNAL There is no doubt that Nageli considered the copper to be in a state of solution, although at first he believed the toxic action of the copper to be due to a new force, ' Isagitat,' and in his original manuscript he uses the word ' isagische ' in describing it, but later he substituted the word ' oligodynamische.' During his investigations which were confined to the action on Spirogyra, Nageli discovered that minute quantities of other metals, viz., silver, lead, tin, iron and mercury, showed oligodynamic properties similar to copper. Many investigators have conducted experiments with copper and its salts, since that time, and one of the most important researches is that of Israel and Klingmann (2), which was published in I897. Israel and Klingmann carried out a large number of experiments on certain bacteria, including Bacillus typhosus and Bacillus coli, many animal organisms and Spirogyra; they used copper foil and found that it had a marked toxic effect on all the bacteria they worked with, B. typhosus being the most easily killed. When the copper solutions containing the organisms were incubated at about 40°C., it was found that they were destroyed in half the time necessary to kill them at laboratory temperature. It was also found that different organisms were differently affected by the copper solution, and although most organisms were killed in a few minutes, some, e.g., Stylonychia, resisted for twentyfour hours, and later experiments by other investigators have shown that some plants not only resist the action of the copper, but even appear to benefit by its presence, under certain conditions. Locke (3) found that the traces of copper contained in water distilled from or through copper vessels were sufficient to kill Tubifex, a freshwater Annelid. The fact that the degree of this toxic action is not constant but varies from species to species in plants and animals naturally suggested the practical application of this effect in the purification of water from deleterious organisms. In I905 an important paper was published by M1oore and Kellerman (4) of the Bureau of Plant Industry of the United States 3I4 ACTION OF METALS UPON BACILLUS TrPHOSUS Department of Agriculture, on a method for destroying or preventing the growth of Algae and certain pathogenic bacteria in water supplies. These authors claim that with very high dilutions of the salts of copper they were able to kill Algae and certain pathogenic organisms ; one part in 50,ooo,ooo killed Algae in watercress beds, I in 4,000,000 foul-smelling Anabaena, and i in IOO,OOO killed both cholera and typhoid in four or five hours at laboratory temperature. Rideal and Baines carried out experiments to contr...
