194 Journal of Agricultural Research vol. xx,No. 3 



fluke, is even more prevalent in Japan and is said by Kobayashi (9) to 

 affect as many as 60 per cent of the inhabitants of some endemic areas. 

 Like malaria and hookworm disease, fluke diseases are comparatively 

 seldom fatal in themselves but are particularly injurious in causing loss 

 of efficiency, reduced vitality, and lowered resistance to other diseases. 

 The long duration and relative incurability of fluke infections are a very 

 serious factor. In this respect fluke infections are far more to be feared 

 than are infections with intestinal parasites, most of which are relatively 

 easy to expel. Of the numerous drugs which have been tried in the 

 treatment of extra-intestinal fluke infections, only tartar emetic, re- 

 cently shown by Christopherson (4, 5, 6, 7) to be more or less specific in 

 its action on Schistosoma, gives promise of being of any great value. 

 No unquestionably effective remedy for lung or liver flukes has been 

 found, and even the use of tartar emetic for schistosomiasis is far from 

 satisfactory, since the serious symptoms of the disease are caused by the 

 eggs of the worms deposited in the tissues and often continue to exist 

 long after the worms are dead. 



With regard to fluke diseases of domestic animals the situation is no 

 less serious. The common liver fluke of sheep and cattle, Fasciola hepatica, 

 is found almost all over the world in temperate climates, being prev- 

 alent wherever these domestic animals are grazed on wet or marshy 

 pastures. In the British Isles, France, Germany, and other parts of 

 Europe and in some parts of the United States, notably western Oregon 

 and Washington and the humid districts of Texas, Louisiana, Florida, 

 and other southern States, the losses from flukes in sheep, cattle, and 

 goats amounts to millions of dollars annually, on account of loss of vi- 

 tality among the animals, depreciation in quantity and quality of meat, 

 and the loss of the infested livers themselves. In the Tropics Fasciola is 

 largely replaced by other flukes — for example, the intestinal Amphistoma 

 and Gastrodiscus, and various blood flukes, Schistosoma. As with hu- 

 man flukes, the extra-intestinal flukes of animals can not be reached 

 readily by drugs, and as pointed out by Ransom and Hall (16) there is 

 still much doubt about the efficacy of drugs which have been recom- 

 mended for use against them, though there is room for much more 

 experimentation. 



On account of the difficulty encountered in treating or curing fluke 

 diseases, preventive measures loom up with even greater importance 

 than they do in dealing with hookworm or other intestinal parasites. 

 The working out of preventive measures based on scientific knowl- 

 edge has only recently become possible, for, although the life history and 

 mode of infection of the common liver fluke, Fasciola hepatica, of sheep and 

 cattle have been well known for a number of decades, such knowledge of 

 human flukes has been acquired only in the past three or four years. 

 Leiper's work on Schistosoma in Egypt in 191 5-1 6 (10), Kobayashi's 

 work on Clonorchis in Japan in 191 5 (9), and Nakagawa's work on 



