206 Journal of Agricultural Research vol. xx, No 3 



SUMMARY AND CONCLUSIONS 



(i) Fluke diseases of both man and domestic animals are of great 

 importance in many parts of the world. They are debilitating diseases of 

 long duration and difficult to treat or cure. Preventive measures, there- 

 fore, are of great importance. The working out of preventive measures 

 based on scientific facts has only recently become possible , since the life 

 histories and modes of infection of the human flukes have been discov- 

 ered only in the last three or four years. 



(2) In all known cases fresh water snails act as intermediate hosts for 

 the important flukes of man and domestic animals. A practical and 

 efficient method of destroying these snails would make the ultimate 

 eradication of fluke diseases, in spite of the difficulty in treating them, 

 a matter of brighter prospect than the eradication of hookworm and 

 other intestinal parasites, in which the sanitary disposal of feces must be 

 relied upon. 



(3) Experiments by the writer, carried out to find some cheap, harm- 

 less method of treating water to destroy snails, demonstrated that copper 

 salts exert a powerful toxic effect upon snails even in very high dilution. 

 In an experiment upon eight species of six families it was demonstrated 

 that copper sulphate in proportions of 1 part to from 500,000 to 2,000,000 

 parts of water destroys snails of all these species within 48 hours; 50 per 

 cent or more are destroyed in dilutions up to 1 to 5,000,000. From the 

 point of view of expense, harmlessness, and convenience in use copper 

 sulphate is preferable to any other substance which has been tried or 

 suggested for destroying snails. The eggs of the snails are not destroyed 

 by the copper salts. 



(4) Copper salts are also highly toxic to algae, fungi, and other lower 

 organisms but are apparently harmless, in the dilutions used, to higher 

 plants and animals, except fish. Water treated with copper sulphate, 

 therefore, is uninjured for drinking, bathing, or irrigation purposes. 



(5) The effectiveness of copper sulphate in water is modified more or 

 less by temperature, alkalinity, dissolved organic matter, and living 

 algae. Some allowance should be made for these factors in estimating 

 the amount of copper to be used in any given body of water. The pro- 

 portion should vary from 1 to 1 ,000,000 in relatively pure water at 20 C. 

 or above to 1 to 500,000 in water which is very cold, is alkaline, contains 

 dissolved organic matter, or harbors an abundance of algae. If the 

 growth of algae is very luxuriant, it would probably be advisable to kill 

 these algae by a preliminary treatment with a 1 to 1 ,000,000 solution of 

 copper sulphate, following this in the course of a few days or a week by a 

 second treatment. 



(6) Copper sulphate can be administered to ponds, reservoirs, or 

 other bodies of standing water in the way advised by Moore and Keller- 

 man for the destruction of algae in water. This method provides for the 



