Lethal effect of long-chain fatty acids on various species of mycobacteria was examined in a buffer of pH 5.6. Oleic, linoleic and myristic acids were most active against all the test strains. Lauric and palmitic acids were also active, but stearic acid was inactive. The unsaturated fatty acids inhibited markedly the activities of the membrane-bound enzymes (acid phosphatase and tetrazolium reductase) of M. bovis. The free fatty acid fraction of “lysosomal components” separated from the normal guinea pig lungs consisted mainly of palmitic (30%), oleic (30%) and linoleic acids (15%) ; consequently the fraction was active in killing mycobacteria. The mycobactericidal activity of free fatty acids was slight at neutral pH and neutralized by a basic protein, protamine. From these observations, discussions were given on the possible conditions required for fatty acids to be involved in the mechanism of resistance to tuberculous infection.
A rapid bio-assay method for α-toxin of Clostridium perfringens was described. The method is principally based on the parallel line assay method, using a stable reference toxin. The method consists of intravenous injections into mice with two dilutions of each toxin sample and a reference toxin, determination of the survival time in minutes, conversion of the time to an appropriate score and calculation of the relative toxicity. The estimated LD50 agreed fairly well with that actually determined. The fiducial limits of LD50 was about 30% when 10 mice were used for each specimen. It became possible to determine the toxicity of 10 samples in a few hours. Mice were more sensitive to the toxin given by the iv route than by the ip route, in contrast to the result of Lynch and Moskowitz (1968) .
Properties of rosette-forming cells (RFC) and plaque-forming cells (PFC) were investigated in a culture of mouse spleen cells with sheep red blood cells (SRBC) . 1) In our culture with good primary response of direct PFC, some differences were noticed regarding the mode of RFC response compared with the in vivo response; the RFC number at the maximum in vitro response was about 1/10 of in vivo one. In addition, the in vitro RFC rarely included RFC with large agglutinates of SRBC which are considered as hemagglutininproducing cells and are rich in the in vivo RFC. These findings indicate that the in vitro RFC contained only a part of the in vivo RFC population. 2) Moderate in vitro RFC response occurred even in the absence of SRBC, while the PFC response was extremely low under the same culture conditions. This suggests that the RFC response was not so specific as the PFC response. 3) The RFC appearing in the culture did not form plaques within 30 min of incubation with complement and SRBC; this showed that the in vitro RFC hardly included PFC. 4) The characteristics of the RFC in the culutre were discussed.
In mature larvae of the fleshfly ligatured tightly at the middle of the body, both anterior and posterior halves failed to pupate in dry condition, where intact larvae usually pupate in 17 hr. When the ligatures were loosened after a certain period, the paralized larvae began to pupate in 16-18 hr. Single injection of ecdysterone of 10μg per g body weight induced full pupariation of the isolated anterior and posterior parts, showing that the blocked pupation in both parts of ligatured larvae is due to prevention of synthesis and secretion of ecdysone in the ring gland. Severance of the peripheral nerves just behind the ganglionic mass or of the recurrent nerves just in front of the proventricle did not show any influence upon the pupation time. Artificial shrinking of the crops did not accerelate pupation in wet condition, nor continuous supply of oxygen reduced the duration till pupation of the anterior parts. When ligations were applied at the level behind the 10th segment larger anterior parts pupated mostly within 40 hr. These results suggest that some humoral factor derived from a certain region in posterior segments, probably located in 11th to the last segments, may play an important role in synthesis of ecdysone at the ring gland.