84 PRESIDENTIAL ADDRESS SECTION D. 



the glands. Many workers have reported them from Japan 

 proper, Yokogawa found them in Formosa and Muto in Korea. 



The small adult fluke varies from 1-5 mm. to 4-5 mm. long, and is 

 from 0"4 to 0"7 mm. broad. The body is covered with nail-like spines, 

 about 10|x long. The oral sucker is from 75^, to 85(x in diameter, and 

 the acetabulum is characteristic, being a sac-like organ situated deep in 

 the body and not opening on to the ventral surface. The testes are 

 elliptical, situated laterally near the posterior end of the body, one slightly 

 anterior to the other. The vesicula seminalis is retort-shaped, and lies 

 transversely, internal to the ventral sucker. The genital sinus receives 

 the openings of the ejaculatory duct and uterus, and opens into a genital 

 pit at the front of the ventral sucker. The ovary is spherical. The 

 vitellaria consist of about 10 acini on each side of the body, and the 

 shell gland lies to the left of the ovary. The uterus forms 3 to 4 large, 

 transverse coils. The eggs are yellowish brown and elliptical, and have 

 no " shoulder " below the operculum as occurs in Clonorchis. They are 

 about 28^, by 16|li. 



The hfe-history has been elucidated chiefly by the work of 

 Yokogawa (1915) and Muto (1917), and its broad outlines resemble 

 those of Clonorchis sinensis. 



The hosts whence Metagonimus gains access to man consist 

 of a trout, Plecoglossus altivelis, and various other freshwater 

 fish, chiefly belonging to the Cyprinidns. The encysted cercarisE? 

 occur beneath the scales and near the fins and tail. Kittens 

 fed on infected fish passed Metagonimus eggs in their faeces in 

 12 to 15 days after eating the fish. Muto in 1917 published his 

 account of the source of infection of the fish. He investigated 

 many molluscs in Korea and found that from 2 to 50 per cent, 

 of those examined harboured cercariie of Metagonimus, the 

 percentage varying with the locality. Melania lihertina is the 

 chief infected mollusc, in which sporocysts, rediae and cercarisE^ 

 are produced. Full details and experimntal evidence are given 

 by Muto. 



The mode of infection of man is by eating infected fish in a 

 raw or imj)erfectly cooked condition. According to Yokogawa, the 

 trout, Plecoglossus altivelis, is a delicacy eaten raw by the 

 Japanese, and his own assistant, who frequently ate raw trout, 

 contracted infection with Metagonimus therefrom. 



Some Other Fluke Infections. 



Recent advances in our knowledge of a number of othei' 

 flukes have been made, but time does not permit of more than 

 a bare note made of them. 



Recently (1921) Nakagawa* has published an account of his 

 researches on the life-cycle of Fasciolopsis huski. This fluke, 

 which may attain the great length of 70 mm., is a parasite of 

 man and of pigs in India, Assam, Siam, China and Cochin-China 

 (among Annamese), and of pigs in Formosa. The eggs hatch in 

 summer, and the miracidia have been proved experimentally to 

 penetrate Planorbis coenosus, Seg'tnentina largiUierti, Planorhis 

 compressus and Limncea pervia. The miracidia develop into 

 sporocysts which produce rediae about 7 days after exposure to 



* An accessible account will be found in Journal of Parasitology, viii, 



pp. 161—166. 



