Adult male mice of CFW strain were divided into 31 groups of 4 mice each and kept for 10 days. The social rank in each group was determinated by observation of mutual fightings during this period and a total number of bite in tail on the 10th day.
Body, adrenal, thymus, testes and preputial gland were weighed for each mouse.
A significant correlation to social rank was found with the weights of adrenal, thymus and preputial gland.
It was found that mice of low ranking had larger adrenal and smaller thymus or preputial gland than mice of high ranking. From these results, it was considered that lowly ranked mice are possibly stimulated more severely by physical and physiological stress as compared to highly ranked mice.

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Comparative studies were made on the selective media for counting the fecal bacteria of 4-to 5-week-old mice. There was no significant difference between the viable counts of enteric bacteria on DHL agar and MacConkey agar. No difference was observed among the viable counts of streptococci on azide agar, SF agar and Mitsuoka's TATAC serum agar.
Mitis-salivarius agar was not suitable for counting the fecal streptococci because the whole surfacewas occasionally covered with other organisms. The viable count of staphylococci on mannite salt agar was in statistical agreement with the count on either Staphylococcus medium No. 110 or Mitsuoka's PEES agar. mannite salt agar was also useful to estimate the number of spore forms of aerobic rods. There was no difference between the viable counts of lactobacilli on LBS agar and modified LBS agar. NBGT blood agar and modified NBGT blood agar were excellent medium for bacteroides while potato dextrose agar was useful for yeasts. At present, there was no evidence on the constant exsistence of bif idus, clostridia, f lavobacteria, pseudomonads or veillonellae in the feces of 4-to 5-week-old mice.
Considering the results obtained and the convenience to prepare the medium, the following media are recommended for the routine examination of fecal flora of mice: DHL agar for enteric bacteria, SF agar for streptococci, mannite salt agar for staphylococci and spores of aerobes, LBS agar for lactobacilli, modified NBGT blood agar for bacteroides and potato dextrose agar for yeasts. However, the viable count on these media never reflect the number of each bacteria estimated from stained preparation.

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