Studies on the migration of the larvae in the body of ddN strain mouse infected with Ancylostoma caninum orally were conducted, and the following results were obtained :
1) The larvae in the mouse after the oral infection migrated through small intestine, liver, lung, pharynx and then reached to muscular tissue, in where they were destroyed gradually.
2) The migration of the larvae from intestine to muscular tissue through finished within 4 to 5days ofter the infection.
3) The larvae were detected in stomach in 15 to 30 per cent, in small intestine in 5 to 10 percent, and in liver in 10 to per cent of the infected number of larvae, in the first day ofter infection.But the number of larvae detected in these organs decreased rapidly in the following day.
4) In lung, the larvae were detected in 25 per cent of the infected number of larvae in the following day ofter the infection and gradually decreased then after.

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As stated in our previous reports, this author considered from comparative observa- tions on the development of experimental murine leprosy, after subcutaneous infection, in various inbred strains of mice that mouse leprosy could be classified into two polar types, benign and malignant. The former type is represented by the case of C57BL/6 strain and the latter type is represented by that of C3H strain.
However, no significant differences were observed concerning the development of visceral lesions between these two strains, C57BL/6 and C3H, after the intraperitoneal infection.
On the other hand, long-term observations, up to 80 weeks, were made in various inbred strains of mice with the subcutaneous infection by the same manners previously examined. From the results of these observations, mouse leprosy should be classified into three types, benign, intermediate and malignant. In the case of intermediate type, newly classified, the leproma at the inoculation site shows the benign feature but the visceral lesion develops severe with time as observed in the malignant case.
Therefore, further long-term observations were made in 7 inbred strains (C3H, CFW, CF#1, KK, BALB/C, C57BL/6 and DDD) of mice, after the intraperitoneal infection, on the development of visceral lesions and survival time of the experimental animals.
Except the cases of DDD strain, the development of visceral lesions showed similar tendency to that observed in the previous experiment, in the cases of these 6 strains. There were no significant differences among these 6 strains, concerning the survival time of mice inoculated with 0.5ml of a 1:100 suspension. In the cases inculated with 0.5ml of a 1:10000 suspension, significant but slight prolongation of the survival time was observed in the cases of C57BL/6 strain which was representative of the benign type after the subcutaneous infection. But no marked difference was observed in survi-val time among the cases of the remaining 5 strains.
In contrast, mice of the DDD strain showed remarkable prolongation of the survival time compared with those of the other strains. Especially, all the DDD mice which were inoculated with 0.5ml of a 1:10000 suspension were survived throughout the ex-perimental period, although almost all the mice of the other strains died at the earlier stage of infection.
It is emphasized from the findings of this experiment that remarkable delay in evolu-tion of the visceral lesions followed murine leprosy infection is a distinctive characteristic of the DDD strain.

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Metacercariae parasitic on the loach living in Ashida River, Hiroshima Prefecture were examined by applying the artificial gastric juice digestion method to twenty loach which weighed from 28g to 46g, As a result, Metagonimus yokogawai was the largest in number, that is, its average number per loach was 18.8 on scales, 3.1 on gills, and 2.8 on muscles. Next to the largest was Centrocestus nycticoracis i.e., 5.1 on gills. Echinostoma cinetorchis, 1.6 on gills. Echinostoma hortense, 2.5 on the inter-ventral membrane. Echinochasmus perfoliatus, 0.9 on gills.
Metacercariae of Metagonimus yokogawai thus collected were given to nine birds and also to five rats for the sake of contrast through mouth in such a way as follows; 50 metacercariae to every five chickens, from 250g to 325g in weight, the same to every two canaries 82g and 88g in weight, the same to every two white-eyes, 46g and 48g in weight and the same to every five rats, from 98g to 120g. Afterwards, observation and studies were made on the number of metacercariae parasitic site, number of eggs in the uterus, first day of ovulation, size of eggs, and developing speed of the body in different hosts.
As a result, of 50 metacercariae given to each host, average 6.4 were detected in the chicken, 6 in the canary, 1.5 in the white-eye, and 17 in the rat. In both the cases of birds and rats, the parasitic site was mainly below the middle part of the small intestine. Difference in the developing speed of the body in different hosts was not perceived. Ovulation began on the ninth day in rat, on the 10th day in chicken, on 18th, in canary, and in the case of the white-eye, ovulation had not yet begun on the 10th day when it was dissected. Average size of eggs taken from 200eggs was 0.0324×0.0208mm.
Hereby the author has decided to name this species as Metagonimus yokogawai takahashii.

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