Myco plasma neurolyticum was found to be harbored in the respiratory tracts of approximately one-half of the mice examined. There was not any significant difference in the isolation rate between mice with chronic respiratory disease (CRD) and apparently healthy ones. The organisms were isolated concomitantly with cultures of M. pulmonis. Though there were small differences in toxicity among the strain of isolates, all these organisms produced neurotoxin for mice, showing the typical rolling symptoms by intravenous injection with broth culture. The maximum amount of toxin produced by this organism was 2^5.5LD₅₀/ml, as determined by intravenous injection to mice with a 24-hr broth culture. The neurotoxicity of the organism was different according to the routes of inoculation, it was higher after intravenous, intraperitoneal and intracerebral inoculations, in this order. NO death occured when injected subcutaneously. Mice of ICR strain were administered intranasally with the culture of freshly isolated strain of M. neurolyticum or a virulent strain of M. pulmonis. M. neurolyticum failed to produce pneumonia, although it was recovered from the lungs of 4 of 10 mice 8 days after inoculation. On the other hand, M. pulmonis proliferated in the respiratory tracts and produced such a characteristic pneumonia as seen in CRD-affected mice. These results suggest that M. neurolyticum may have nothing to do with pneumonia production, though it has been isolated frequently from the respiratory tracts at naturally infected mice.

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Female ICR: JCL mice were reared in wire-mesh cages with nozzles for automatic water supply on a battery with an automatic washing system, and the evaluation of this system was made in comparison with the conventional feeding system with water bottles, alumite cages and changes of the bedding. In weight gains, feed intakes, water consumption, leucocyte and erythrocyte counts, hematocrit values or vaious organ weights during the period from 3 to 14 weeks of age, animals maintained by the automatic rearing system showed no significant difference as compared with those maintained by the conventional system, providing evidence for a conspicuous labor saving with the automatic control system.

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Mature female mice (ICR-JCL), 8 to 12 weeks of age, were artificially inseminated at 8: 30—9: 30 a.m. on the day of estrus vaginal smear (about 3-7 hr after ovulation) with 3.18×10⁶, 1.83×10⁶ and 1.15×10⁶ sperms from four, two and one cauda epididymidis, respectively, of adult males which were suspended in 50 μl of a modified Krebs-Ringer-bicarbonate solution and incubated at 37°C was under 5% CO₂ in air for an hour. Immediately after insemination, pseudopregnancy inducd by an artificial penis and a vaginal tampon. Out of 13 females inseminated with 3.18×10⁶ sperms, 9 females showed placental signs and 8 of them gave birth to the mean 10.5±2.20 (M±S.D.) young at term. Four of 13 females having received 1.83×10⁶ sperms became pregnant giving birth to the mean 4.3±2.1 (M±S.D.) young at term. On the other hand, 5 out of 6 females failed to become pregnant following insemination with 1.15×10⁶ sperms, and only one showed a placental sign and gave birth to twelve young at term. It is concluded that the conception rate and litter size are both dependent on the number of sperms inseminated and that more than 3×10⁶ sperms are necessary to get the conception rate and the litter size comparable to those in natural mating.

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The temperature of various positions in an occupied animal room (mice, rats) including inside of cages were measured using a 50 channels thermal data recorder (step time 0.5 sec, 5 min intermittent through 24 hr and continuous) in a summer day. Any short periodical fluctuation of room temperature had practically no influence on the inside temperature of plastic cages. Against small diurnal flactuations, stable vertical gradients (about 1°C between tops and bottoms of racks) were observed amonng one hour averages of room air temperatures. Air temperature in the cage fluctuated in larger scale. (up to 3°C) For controlling animal room temperature, each of short periodical fractuation, diurnal change and spasal distribution should be separately concerrned.

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The usefulness of simplified techniques in sampling of individual mouse and rat sera and their shipping in wet state for serological checking of infections were described.

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