The effects of the outermost structure of the muscle cells on ionic movements or contents were investigated with reference to the movement of membrane Ca⁺⁺ when the membrane of the sartorius muscle of the frog or toad was disturbed (1) mechanically by stretch, (2) mechanically by soaking with hypertonic Na Ringer, and (3) chemically by treating with trypsin.1. In Ringer, 130% stretch of the muscle for 24 hours resulted only in a slight increase in internal Na. Ion contents of the muscle, while 140% stretch in trypsin-Ringer, were the same value as those unstretched and in the same solution. Accordingly, stretch in such a ratio caused no morphologically significant changes even after immersion for 24 hours.2 . Hypertonic medium, 200 mM Na, showed the depolarization of 15 - 20 mV and a transient increase in Ca⁴⁵ efflux. The Ca⁴⁵ efflux was varied proportionally by changing external Ca concentration. Because this effect of hypertonic Ringer on Ca⁴⁵ efflux can be additive to Ca⁴⁵ efflux increase produced by another depolarizing agents the membrane sites from which Ca ions are released in hypertonic solution may be different from the membrane sites which dissociate Ca ions under other conditions.3. Trypsin caused the increase in internal Na and the decrease in internal K, and this pattern resembled the picture of facilitated diffusion which is similar to cation movements observable in K free Ringer. Ionic changes were simultaneously followed by both depolarization and an increase in Na²² fluxes, but no immediate correlation with the dissociation of membrane Ca⁺⁺ was detected. The changes in trypsin-Ringer were Ca-independent. Although the conditions to demonstrate the membrane depolarization are generally supposed as those which increase Ca⁴⁵ efflux the treatment with trypsin shows no such close interrelationship.

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In Japan, the main effort for the control of schistosomiasis has been directed at the control or eradication of vector snail, Oncomelania hupensis nosophora (Robson) since prior to World War II. One of the principle methods for control is the periodic application of molluscicides. Initially lime was used in Katayama under the guidance of Prof. Fujinami and then during World War II Ca-cyanamide was used. After 1954, sodium pentachlorophenate has been used in all the endemic areas. Cementing of irrigation ditches has been adopted in Japan from 1954 as another mean on control. In 1956, a ten year project of cementing all ditches in the endemic areas was planned with the financial aid of the Government. However by 1966, only about 50% of all ditches in the endemic areas had been replaced by cemented ones.Nagatoishi-cho, a part of Kurume City, has a population of 834 persons. The area consists of 20 hectare and is surrounded by a dike which was a part of the Chikugo River. Most inhabitants of this area are farmer. In 1948, Hunter et al. found that 72. 9% of them were infested with Schistosoma japonicum. The area was sprayed twice a year with sodium pentachlorophenate in 1950 and 1951. At the termination of the two-year experiment in December, 1951, it was found that the snail had not been completely eliminated from thee paddies and irrigation ditches. In July of 1953, a large flood occurred and all houses in the village were immersed in muddy water and the dike surrounding the village was broken in three places.In 1954, the cementing of the ditches started and was finished in 1958. A reduction in infection rate of school children resulted with the progress of the cementing.Today, no Oncomelania snail can be found inside of the dike, but many infected snails are still found outside of the dike and on the Chikugo River bed. Since 1965, field mice and voles inhabiting in the latter area have been examined for the natural infection with Schistosoma japonicum. A survey was conducted in the spring of 1966. Intradermal test with antigens prepared by Coca's method using adult worms of S. japonicum was applied to the inhabit-ants of the village. Those with positive or doubtful reactions were examined and examinations for parasite eggs in their stools were conducted.In the present paper, we are reporting a part of results of our recent above-mentioned surveys.

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Scharrer (1928) first described the function of neurosecretion in the nucleus preopticus of the hypothalamus of Phoxinus Laevis concerning the morphology of the nucleus preopticus of fishes. Later Palay (1945) reported that there is a topographical relation between the nucleus preopticus and the neurohypophysis in fishes (Catfishes, Ameriurus nebulosus, Ameriurus melas, Noturus flavus). This finding is supported by Hild (1951). Many researches on the hypothalamic neurosecretory system in fishes have been done by light microscopy (Scharrer, 1930, 1932, 1636, 1952, ; Florentin, 1934; Mazzi, 1941; Stutinsky, 1953; Bargmann, 1953, ; Stahl, 1953; Enami, 1954, 1955, Kobayashi et al., 1960; Szabo et al., 1965; Sathyanesan, 1966). While electron microscopic studies on the hypothalamic neurosecretory system in fishes have been reported by Palay (1960, goldfish), Lederis (1960, cod), Follenius (1963, truite, perche), and others. Hitherto we have examined, in the light of comparative anatomy, the neurosecretory cell of the hypothalamus in mammals, reptiles, and amphibians with the electron microscope (Murakami, 1962, 1963, 1964). Thus this paper will present the neurosecretory cell of the hypothalamus in fishes.

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