212 THE FLUKES 



tube of an aquatic animal, another in the conjunctiva! sac in 

 the eyes of birds. 



The flukes which infest man may be divided for convenience 

 into four groups, the blood flukes, the lung flukes, the liver 

 flukes and the intestinal flukes. Altogether over 20 different 

 species have been found in man, but only those which are com- 

 mon or important will be considered in the following pages. 



Control. In all known cases freshwater snails act as inter- 

 mediate hosts for the flukes which infest 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 brigher prospect than the 

 eradication of hookworm and other intestinal parasites, in which 

 sanitary disposal of faeces must be relied upon. 



Recent experiments by Chandler show that copper salts exert 

 a powerful effect upon snails, even in very high dilution, appar- 

 ently acting by inhibition of necessary enzymes. In experi- 

 ments on a number of snails of six different families, including 

 members of all the families of which species are known to act as 

 intermediate hosts for pathogenic flukes, it was demonstrated 

 that copper sulphate in proportions of one part in from 500,000 

 to 2,000,000 parts of water destroys the snails in all cases within 

 48 hours. 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. 

 In the dilute solutions which are necessary the water is not in- 

 jured either for human or animal consumption, for bathing, or for 

 agricultural purposes. It is destructive to very few other or- 

 ganisms in the water, except algae. It is, however, injurious to 

 some species of fish, especially the young, and its use may be 

 objected to for this reason in some places where fluke diseases 

 are prevalent, e.g., in oriental countries, where fish are extensively 

 kept in the snail-infested waters and form an important part of 

 the native diet. The eggs of the snails are not destroyed by the 

 copper salts. With government aid and supervision, the work 

 being carried out under the direction of scientifically trained 

 men or commissions, it seems entirely possible that whole states 

 or countries, at least in the vicinity of towns or villages, could be 

 freed of human fluke diseases. 



