A series of experiments on various factors which induce optimal in vitro excystation of the metacercariae of Metagonimus yokogawai isolated from the fish, Plecoglossus altivelis was conducted and the following results were obtained. The metacercariae used in this experiment were isolated by the digestion technique therefore all of them were pretreated with the acid-pepsin solution before being applied to the various tests. No excystation occurred when the metacercariae were placed in a salt solutions such as physiological saline, Tyrode solution and Veronal, Tris buffers alone or in combination. The metacercariae underwent complete excystation in the trypsin and pancreatin solution in Tris buffer within an hour at 38 degrees C. The best results were obtained in 0.8-0.9% trypsin solutions, pH 8.0-8.6 and at 38-40 degrees C, approximately one hundred per cent excystation occurred in 40 minutes. Not only temperature but also hydrogen ion concentration played an important role causing excystation of the metacercariae in trypsin-Tris buffer solution. However, bile salts were not responsible for the excystation. Agitation effect on the excystation was tested as a mechanical stimulus and it was found that the shaking stimulus accelerated the excysting mechanism, compared with the metacercariae on which it was not imposed. It is concluded that the metacercariae pretreated in the acid pepsin solution demonstrates an essential requirement for the enzyme solution such as trypsin or pancreatin, provided with the optimum conditions of temperature and hydrogen ion concentration in excysting medium.

A single dose of Tetramisole, 2.5 mg/kg body weight, was given to the infected cases of intestinal parasites. The number of cases were: Ascaris lumbriocides 96, hookworm 16, Trichostrongylus orientalis 10, Trichocephalus trichiurus 114 and Clonorchis sinensis 19. No dietary restriction before and after the administration of Tetramisole was required. In Ascaris infection the egg negative conversion rate and the egg reduction rate were 92.7 per cent and 99.5 per cent, respectively. In Trichostrongylus orientalis infections, 9 out of 10 cases were resulted egg negative after the single dose of Tetramisole, and hookworm, 12 out of 16 administered showed egg negative. However, there were no appreciable effectiveness to the cases of Trichocephalus trichiurus and Clonorchis sinensis. Mild and transient side effects were noted in 75 cases (54.5%) out of 140 cases. The main symptoms were dizziness (25.5%), anorexia (25.5%), abdominal pain (18.6%), diarrhea (16.6%), headache (15.2%), nausea (14.4%) and fever (11.0%). From the above results, it is anticipated that Tetramisole is an effective anthelminthic for elimination of Ascaris, Trichostrongylus and hookworm.

This study was conducted to study the life cycle of Haemaphysalis bispinosa and Boophilus microplus. The results obtained are summarized as follows. The period of blood-sucking from a host was 20-25 days (average 22.5 days) for Haemaphysalis bispinosa and was 28-43 days (average 35.5 days) for Boophilus microplus. The parasitism period of Haemaphysalis bispinosa on the host was the same as the blood sucking period, but the parasitism period of Boophilus microplus was only 20-23 days (average 21.5 days) because the Boophilus microplus molted its skin while still on the host. The period from hatching to death for Haemaphysalis bispinosa was 73-123 days (average 101 days) and was 63-92 days (average 77.5 days) for Boophilus microplus. The ticks were waiting on the grass for their host. I could find ticks especially on miscanthus purpurascens, braken, and miscanthus grasses. Larvae had climbed to a height of 15-35 cm and there formed groups of 500. Young adults had climbed to a height of 80 cm and there formed groups from 1 to 5. The number of eggs laid was 2,452 by Haemaphysalis bispinosa and 2,836 by Boophilus microplus. Larvae could not survive the winter. Nymph and young adults of Haemaphysalis bispinosa survived the winter. Boophilus microplus survived the winter as eggs.

Total 9 cases of extraintestinal amoebiasis, amebic liver abscess and amebic lung abscess, were treated with metronidazole. The diagnosis and progress check were done by (1) stool examination, (2) size and pain of liver, (3) hematological examination, (4) urinanalysis, (5) X-ray or liver scanning (6) examination of aspirated pus from liver and (7) immobilization test of E. histolytica. Results are summarized as follows: Amebic hepatitis: Metronidazole was given to 3 cases with daily dose of 0.9-1.2 gm for 3-7 days. Clinical symptoms were completely restored by the treatment. Amebic lung abscess: One case was treated with metronidazole for 3 days with the daily dose 1.2 gm. X-ray findings showed remarkable improvement by the treatment. An additional administration of the drug for 6 days resulted complete resolution of the pneumonic changes. Amebic liver abscess: Four cases were treated with metronidazole. The daily doses were 0.4-2.4 gm and continued for 2-10 days. Aspiration of the abscess for 1-10 times or continuous drainage of pus were performed during the course supplementarily. All cases were recovered to normal by the combining treatment. No remarkable side effect was noticed by the drug administration, and no relapse was experienced up to date.

During the period from May to October 1969, the authors carried out a series of tests with the aim to ascertain the present status of susceptibility of adult cockraoches to various insecticides. The tests on the susceptibility of cockroaches to dieldrin, D.D.V.P., Diazinon; Dibrom, Malathion and lindane were performed with the topical application and the residual film methods under the conditions of 26 degrees C and 80% of relative humidity. The insects tested were collected from Seoul City and were reared at the laboratory. Some of the important results so far obtained can be summarized as follows: The median lethal doses (LD(50)) of the five insecticides against female adult cockroaches were: 0.4 ug/roach or 4.02 ug/body weight (gm) by Dieldrin, 0.29/roach or 2.88 ug/body weight (gm) by D.D.V.P., 0.29 ug/roach or 2.96 ug/body weight (gm) by Diazinon, 0.54 ug/roach or 5.37 ug/body weight (gm) by Dibrom, and 2.96 ug/roach or 29.60 ug/body weight (gm) by Malathion. And those against male adult cockroaches were: 0.18 ug/roach or 3.29 ug/body weight (gm) by Dieldrin, 0.27 ug/roach or 4.89 ug/body weight (gm) by D.D.V.P., 0.16 ug/roach or 2.91 ug/body weight (gm) by Diazinon, 0.49 ug/roach or 8.97 ug/body weight (gm) by Dibrom, and 1.32 ug/roach or 24.19 ug/body weight (gm) by Malathion. The level of susceptibility of adult cockroaches to the insecticides tested was 1.0-1.6 times higher as compared with the results obtained on the Japanese Takashi strain. The median knockdown times (LT(50)) of the female adult cockroaches by insectcides at 1% concentration of 3 mg per square centimetre were 1.82 hours by Malathion, 1.36 hours by Diazinon, 0.56 hours by Lindane, 0.50 hours by Dibrom, and 2.56 hours by D.D.V.P. A marked difference was seen to exist between the males and the females. The female cockroaches were more resistant than the male to Dieldrin, Diazinon and Malathion.