[in Japanese]

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The regular 4 days oestrous mice(4 CS)were established by selective inbreeding of ddN descendant.The effects of environment on the oestrous cycle of the 4 CS, ddN and CF#1 strains werecompared.
1)In ddN and CF#1 strain mice caged in group the oestrous cycle determined by vaginalsmears were shortened in the presence of males than when males were absent, as reported by Whitten, and a little mice were showed regular oestrous cycle in the presence of males.
2) In the absence of male, the individual caging mice revealed oestrous cycles frequently as well as reported Whitten. In addition the authors observed that the female group adherent to male's excrement repeated more regular oestrous cycles than the group adherent no male's excrement.
3) The effect of the control of lightning on the regularity of oestrous cycle was recognized to a certain degree in the mice caging individually.
4) The regularity of oestrous cycle was revealed by environmental arrangement in the ddN and the CF# 1 mice, however only small animals repeated regular cycles in 40 days of observation period.
5)The 4 day cyclic mice (the 4 CS strain) bred by us repeated cycles regularly under the con-ditions of natural weather or absence of the male, under which other strain mice revealed irregular cycles.

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Using the Wistar strain rats, the authors investigated the effect of deciduomata on the duration of pseudopregnancy.
Pseudopregnancy was induced by mating with vasectomized males. The first day of vaginal diestrus after mating was designated day one and the last day of the successive diestrus the last day of the pseudopregnancy. Deciduomata was induced by traumatization of the endometrium on the 4th day of pseudopregnancy.
The average length of pseudopregnancy of the rats bearing the massive deciduoma in the bi-lateral uteri was significantly prolonged to 18.3 days, compared with 12.9 days of the sham-operated control rats. On the other hand, no significant prolongation of pseudopregnancy was observed in the rats bearing uni-lateral deciduomata.
In the bi-laterally traumatized rats, no regressive corpus luteum was observed on the 13th day of pseudopregnancy, though some of the corpora lutea of both the sham-operated and the uni-laterally traumatized rats exhibited already a retrogressive aspect at this time. Moreover, on the 13th day of pseudopregnancy the weight of the decidual uterus of the uni-laterally traumatized rats was significantly smaller than the uterus of the bi-laterally traumatized rats.
These observations indicate that the induction of deciduoma in the bi-lateral uteri prolongs the life-span of corpora lutea and that when the uni-lateral uterus was left without treatment their corpora lutea might regress at the normal time.

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1. Morphological and Chemical analysis was made in semen of six Holstein bulls from 5 to 17 months of age, to determine the age of sexual maturity. Semen was collected once a week by the electrical ejaculation and evaluated on the following characteristics : volume, pH, concentration of spermatozoa, sperm count per ejaculate, initial motility and percentage of live spermatozoa. In addition, the concentration of fructose, total nitrogen, ascorbic acid, acid-soluble phosphorus, calcium, sodium, potassium and chlorine in semen were estimated.
2. Puberty in the bulls as shown by the appearance of motile spermatozoa in semen, was in average 8. 5 months of age. The volume of semen was less than 2.5ml before 12 months of age. At 13 months, mature values were recognized in the sperm count per ml and per ejaculation, as 4×10⁸ and 10×10⁸, respectively. Sperm motility showed 50 in the index of motile sperm at 11 months. pH showed above 8.0 before 6 months, then gradually decreased to below 6.8 after 10 months of age.
3. Seminal fructose did not appear until bulls reached 5.3 months of age in average. At 9 months, more than 500 mg of fructose and total nitrogen, and 19.5 mg of calcium were evaluated in the 100ml semen. 35 mg of acid-soluble phosphorus and 6.5 mg of ascorbic acid were evaluated in the 100ml semen at 13 and 14 months of age, respectively. Chlorine was more than 400 mg in 100ml before 8 months of age, thereafter it decreased to less than 270 mg at 11 months. Sodium and potassium in semen showed an almost constant value throughout the experimental period.
4.These results shows that the age of sexual maturity in Holstein bulls is 13 or 14 months.

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