Drug sensitivity test of bacteria is practically made by bringing a certain mass of bacterial cells into contact with a given drug. This bacterial population is considered, however, to consist of the cells which are not constantly the same in various biological characteristics including drug sensitivity. Therefore, according to the size of inoculum and the period of incubation, the minimum inhibitory concentration of drugs to bacteria often shows variations in some range. In addition, there must be much possibilities that bacteria as a mass show a somewhat different behaviour against chemotherapeutic agents from that of a single cell. In this connection, the present authors attempted to analyse streptomycin sensitivity of a strain of E. coli by single cell cultivation technique and further to examine the mode of development of streptomycin resistance by this method. This way of experiment has ever been devised by Sakamoto (1954) .

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In the summer, 1955, outbreaks of food-poisoning due to marine products, especially to squid, took place throughout Hokkaido. The number of patients reached about 3, 000, a half of which were caused by squid.
The most eminent features of these food-poisonings were as follows :
(1) Clinical symptoms observed were, for the most part, transient nausea, vomiting, abdominal pain and diarrhoea. The length of incubation period was variable, from 1 to 24 hours. The morbidity rate varied from 10 to 100 per cent. Prognosis of the disease was usually benign and the majority of the patients recovered in about 12 to 24 hours.
(2) Food responsible for the outbreaks was, for the most part, various marine products such as squid, poulp, tunny, mackereletc.Above all, squid, especially sliced raw squid, was the most important vehicle in the outbreaks.
(3) Bacteriological examination carried out on the implicated foods and the feces of the patients failed to determine any definite bacteria as the causative organisms. A small number of strains of Shigella, Arizona, Citrobacterand pathogenicEscherichia coliwere isolated. Though clinical signs and symptoms had strong resemblance to staphylococcal food-poisoning, the results of the laboratory examination on hemolytic staphylococci were negative in most of the materials.
(4) The frequency of the outbreaks raised in proportion to the height of the atmospheric temperature. In 1955, unusually high temperature continued in July and August, during which almost all of the outbreaks took place.
In consideration of the features above described, the authors proposed a working hypothesis on the pathogenesis of these fish-borne summer food-poisonings. If the activity of cholinesterase (Ch-E) which decomposes acetylcholine (Ach) was inhibited by some agents, Ach would be accumulated to a level on which it exerts its irritating action on the digestive canal. The following facts will support this view.
(1) It is well known that administration of Ach brings about nausea, vomiting, abdominal pain and diarrhoea in men.
(2) These symptoms are observed in mild cases with poisoning due to organic phosphorous insecticide such as “parathion”. One of the present authors (Iwamoto, 1955) reported that serum Ch-E activity is markedly inhibited in these cases.
(3) Serum Ch-E activity usually decreases in hot seasons (Okinakaet al., 1953) .
To sum up, the following hypothesis was proposed by the authors on the pathogenesis of these fish-borne summer food-poisoning. If in the summer seasons when the activity of serum Ch-E was at a low level, some unknown agents which inhibit the enzyme activity were brought into or produced in the digestive canal, decrease in the enzyme activity would be locally caused, thus result-ing the accumulation of Ach which would give rise to variable digestive disturbances.
In order to confirm the validity of this hypothesis several experiments were carried out in this laboratory. The present paper deals with the comparative study on the serum Ch-E activity of the patients with that of the normal healthy persons.

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As was already described in the first report (Iwamoto et al., 1957), serum cholinesterase (Ch-E) activity in the patients with fish-borne summer food-poisoning was lower than that in normal healthy persons. The next point is to clarify the mechanism by which this decrease in Ch-E activity is brought about. The authors have searched for the possible presence of inhibiting agents in culture filtrates of various intestinal bacteria.

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In the preceding papers (Nishida, 1954a, b) the author demonstrated with static culture ofC. diphtheriaeP. W. No. 8-Tronto strain that diphtheria toxin was excreted during the stage of growth in which the most important enzyme systems of this organism were losing their activities, being followed by the increment of dead cells. Yamanaka (1954), however, demonstrated with its static culture in P. L. O. medium (Ozaki, 1953) that there could not be found so much increment of dead cells as that shown by the author. The author (1954c) also demonstrated with its shake culture in Pope's medium that the toxin could be released without the increment of dead cells.
Mitsuhashiet al. (1951) stated from the results with shake culture ofC. diphtheriaethat the most available conditions forr the growth of this organism were the most available conditions for the toxin production, provided that the medium was deficient in Fe''-ion. In 1954 Barksdale and Pappenheimer demonstrated with shake culture that the toxin production could be seen already in the stage of logarithmic growth of this organism. In 1955 Yoneda and Pappenheimer stated moreover that the toxin release was caused before the cell lysis, because no noticeable release of nucleic acid could be found in the course of the toxin excretion. The release of diphtheria toxin from the intact cells, however, is unlikely to take place in situ, because the molecule of diphtheria toxin is known to be too large to pass the intact cell membrane.
In this report the authors investigated on the relation between the toxin excretion and the grade of degeneration in the course of shake culture which did not yet show any increment of dead cells. These preliminary steps of degeneration were detected by testing the integrity of functions of its constitutive enzymes as much as possible.

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In 1947 Pappenheimeret al. claimed concerning the mechanism of diphtheria toxin production that toxin was excreted as failure products of synthesis toward iron porphyrin enzymes. In 1951 Freeman demonstrated that nontoxigenic strains ofC. diphtheriaewere converted into toxigenic strains by lysogenization with its phage. It is not yet, however, clarified why this toxin molecule produced can be released so early into the medium or even in the logarithmic phase of the growth (Barksdaleet al., 1954) . Recently Hatano (1956) showed that the toxin was released not at the same time with the cell lysis by its phage but just a given time later than the phage issue into the medium.
In the preceding report (Nishidaet al., 1957a) the authors demonstrated that the enzyme activities ofC. diphtheriaewere easily denatured by a few conditions in the course of its shake culture. Since these findings suggested to the authors that diphtherial cells might have a more liability to degenerate in water than those of other species of microorganisms in spite of its strong resistance on solid medium or in dry circumstance (Kolleet al., 1928), an investigation was undertaken to see the stability of young cells ofC. diphtheriaesuspended in water by testing the activities of its constitutive enzymes as much as possible and by testing released protein from suspended cells. The former is described in Experiment I and the latter in Experiment II.

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The tapeworms dealt with in the present paper were recovered from a Ceylon domestic fowl, Gallus gallus domestics, and sent to me far examination by S. P. Vernando, University of Ceylon, Peradeniya, Ceylon.
The author, investigating the tapeworms, found that the tapeworms were of new species belonging to GenusRaillietina, SubgenusRaillietina, which have not hitherto been recorded from domestic fowls.

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Reports that have been accumulated by many investigators on ascaris spermatozoon, are able to be divided into two. One is studies on chromosomes of ascaris male pronucleus. Such investigation originating in the work of Bon-nevie (1902) onAscaris lumbricoides, was followed up by Boveri (1910) onA. megalocephala, Edwards (1910), Jeffery and Haetl (1938), and Walton (1924) on the former specimen. But these author's reports were not on the whole process of ascaris spermatogenesis but on the chromosome number, form, and behaviour in its reduction division. The other is studies on its spermatogenesis itself: Bischoff (1855) and Thomson (1856) had observed spermatogenesis inAscaris mystaxand Beneden and Julin (1884), Scheben (1805), Mayer (1908), and Romieu (1911) had made information on that ofAscaris megalocephala. Especially on the work of Mayer (1908) he observed the vicititude of mitochondria in the cytoplasm of spermatocytes and described the formation process of so-called‘Glanzkörper’which was one of characteristics of ascaris spermatozoon morpho-logically.
Materials that have been studied on nematode spermatogenesis were only three species, A. mystax, A. megalocephala, andSprina parasitiferawhich was investigated by Cobb (1928) as a free living marine species. No reports on that ofA. suillawere, therefore, available and the peculiar form of its spermatozoon has attracted the author's attention during our previous studies on its ovogenesis. These two facts furnish the reason why the present study has been undertaken.

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The previous report from this laboratory (Yoshino, 1956) revealed that the 1-day old hen's egg was capable of supporting growth of herpes simplex virus. Later, it was found that the 1-day egg was also susceptible to rabies (Yoshino, Kuma, Kondo and Kitaoka, 1956), vaccinia (Oya, 1956), variola (Oya, 1956), Japanese B encephalitis (Matumoto, 1957), and Rift Valley fever viruses (Matu-moto, personal communication) . An interesting observation common to all these cases was that a few infectious units as measured in other susceptible hosts could initiate an infection in the 1-day egg and that the quantity of virus yielded per egg was as high as, or in some cases even higher than, usually obtained in older eggs.
In the above-cited experiments with herpes virus, egg-white of infected eggs was replaced with saline and a considerable amount of virus appeared in the saline portion over a couple of weeks following infection. The egg-white replacement technique was thought to be of use for obtaining a satisfactorily pure viral suspension, and applications of this technique to various practical purposes were thought about. In this connection, it was desired to supply detailed information concerning the fundamental aspects of host-virus interrelations in this system.
Thus, the experiments to be reported herein were undertaken to elucidate (1) quantitative relations between invading virus particles and susceptible cells, (2) change in blastodermal tissue, especially in cell number, after infection, and (3) reproducibility of viral titers in the saline as well as in the yolk portion over a prolonged incubation period. The results obtained eventually proved that this simple system could be regarded as a new type of tissue culture.

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