196 Journal of Agricultural Research vol. xx, N0.3 



exterminating snails would be practical on a large scale, either on account 

 of the prohibitive cost or on account of the excessive amounts of the 

 material used and consequent injury to the water for drinking, bathing, 

 or irrigation purposes. 



In the hope of finding some effective means of destroying disease- 

 carrying fresh-water snails a series of experiments was undertaken by the 

 writer. The original purpose of the investigation was to find a solution 

 to the liver fluke problem among sheep and cattle raisers in the Willa- 

 mette Valley of Oregon, but it was realized that if a means of controlling 

 all fresh-water snails could be found, the results would be of infinitely 

 greater value than the solution of the local problem, and the experiments 

 were carried on with this in mind. 1 



It was obvious that any chemical which could be used on a large scale 

 for the destruction of snails in ponds, marshes, or streams must not be 

 toxic to man or domestic animals in the dilutions used and must not be 

 expensive. An attempt, therefore, was made to find a cheap chemical 

 substance, readily soluble in water, which would be destructive to snails 

 in relatively weak solutions and which would not render water either 

 injurious or unpalatable for man or domestic animals. 



The chemicals which were selected for preliminary experiments, the 

 dilutions which were made, and the results obtained are shown in Table I. 

 The snails, Limnaea (Galba) bulimoides, 2 were immersed in each solution, 

 using chemically pure salts and tap water, Corvallis tap water being 

 unusually clear, pure, and soft. The sign — indicates no evident effect, 

 ± slight noticeable effect in behavior, + distinct illness without com- 

 plete prostration, + + complete prostration, and © death. It was found 

 later that snails which were apparently dead would sometimes revive if 

 placed in fresh, aerated water; therefore the results shown in this table 

 are not absolutely dependable. They do, however, demonstrate beyond 

 question one striking thing — the fact that copper salts have an extremely 

 toxic effect on these snails, even in such great dilutions as one part to a 

 million of water. Mercuric bichlorid is the only other salt experimented 

 with which approaches the salts of copper in its toxicity to snails, but 

 since it is evidently not so effective as copper, is more toxic to higher 

 animals, and is more expensive, no further experiments with it were 

 carried out. 



The salts of copper being evidently the most promising substance with 

 which to attack aquatic snails all subsequent work was concentrated on 

 them. Experiments with various copper salts (CuCl 2 , CuS0 4 , Cu[N0 3 ] 2 ) 

 were tried, and it was found that with equivalent concentrations of the 

 Cu ++ ion their toxicity was approximately the same. Copper sulphate, 



1 The writer has been unable to get access to the following paper: Germain, L. de l'EFFET des poisons 

 min£raux sur quelques moiausques terrestres et fluviatiles de France, In Bui. Soc. Amis Sci. 

 Nat. Rouen, s. 4, ann. 34, 1898, sem. 1, p. 71-78. 1899. 



2 Snails specifically named in this paper were kindly identified by Dr. H. A. Pilsbry, Dr. F. C. Baker, 

 or Mr. Bryant Walker. 



