Fecal Escherichia coli strains isolated from laboratory animals such as mice, guinea pigs and rabbits were examined for drug resistance and detection of R factors. The results were as follows. 1) Of 166 strains isolated, 25 strains (15.1%) were resistant to either one or more of the six drugs, aminobenzyl penicillin (APC), streptomycin (SM), kanamycin (KM), chloramphenicol (CP), tetracycline (TC) and nalidixic acid (NA) (Table 1) . 2) Of 22 resistant strains of E. coli isolated, except three SM·KM·NA-resistant strains, 21 strains (95.5%) were found to have transferred part or all of their resistance patterns (Table 2) .)

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The influence of autoclaving at 127°C for 30 min on nutritional components in the CL-2 diets and the differences in the results of metabolism tests in ICR strain conventional mice given non-autoclaved and autoclaved diets were observed. The results were as follows : 1) General composition and several fatty acids content did not show any major differences between the two diets. Amino acid components of autoclaved diets were less than those of non-autoclaved diets except in the case of threonine and isoleucine. Determination of three kinds of vitamins, i, e. A, B₁ and E, showed losses due to autoclaving. The loss of B₁ was especially remarkable. 2) Body weight, food intake and fresh feces excretion were not much different in both cases. Fecal nitrogen (N) excretion per unit N intake showed a tendency to decrease in mice fed non-autoclaved diet, but urinary N excretion did not show this tendency. Protein N (trichloroacetic acid precipitable N) in feces was less in the case of non-autoclaved diets than in the case of autoclaved diets, but amount of non-protein N per unit N intake did not show the same tendency. 3) Apparent digestibility of crude and true protein in mice fed non-autoclaved diet increased remarkably in comparison with that of mice fed autoclaved diet except a few example, but the digestibility of crude fat was not much different in both cases. 4) N retention and apparent biological value of mice fed non-autoclaved diets was higher than that for mice fed autoclaved diets.

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A technique of ovarian transplantation in mice was described. The operation was done under dissecting microscope using the ophthalmo-instruments and the electro-knife refering to the method by Palm Joy. The sites and methods for cutting the ovarian capsule and ovary of the host animal were shown in Fig. 2 and 3. About a half of the ovarian transplantation was successful by our techniques. In a few cases, however, the ovary of the host animal remaind. Pregnancy rate and mean number of embryos in the three inbred strains of mice subjected to the ovarian transplantation were 58.8% (10/17 animal) and 4.7 in BALB/c, 80.0% (16/20) and 3.8 in C3H/He and 71.4% (10/14) and 5.5 in C57BL/6, respectively. Reproductive perfomances of muscular dystrophy mice (C57BL /6J-dy) subjected to the ovarian transplantation were 56.8% (31/55) for pregnancy rate, 4.1 for litter size and 3.1 for mean number of weanlings. Although these values are still low and it is necce-ssary to continue investigating the transplantation techniques, the maintenance and production of muscular dystrophy mice by this method might be possible.

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For the purpose of increase of work efficiency and uniformity of feeding conditions, management system has been improved since 1964 without any reconstruction and adjustment of animal room itself. The mainly improved points were as follows ; introduction of the cage racks for rats, hamsters, guinea-pigs and rabbits accompanying with the equipments of automatic supply and drainage of water (Figs. 3, Photos. 2, 3 and 4), the cages suitable for use of wood shavings and the equipments of water supply for dogs and monkeys (Fig. 4, Photos. 5 and 6) . By employing the new system, the time required and labor consumption for management were decreased to 1/4 and 1/20, respectively, when compared to the case of the old system (Fig. 5) .

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The conditions of sterilization were examined for preparing the aseptic materials using the autoclav e equipped in the Breeding Section of Laboratory Animal Center. Sterilized diets could be prepared by autoclaving at 115°C for 30 min, at 120°C for 20 min or at 125°C for 15 min. Food intake and body weight increase in mice given the autoclaved diet were not different from those given untreated diet, although dietary vitamin B₁ contents reduced to 20-50% of untreated diet after autoclaving. A longer period of autoclaving was necessary to sterilize the drinking water, because of a large value in the specific heat of water. In practice, sterilization of water was required for autoclaving at 120°C for 90 min, while the sterilization of bedding, cage and other materials as well as diet for autoclaving at 120°C for 20 min. [Exp. Animals, 22 (1), 31-36, 1973]

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