Unpedigreed white virgin mice were mated with mature male mice from the same colony. Five groups of copulated female mice were treated with a single intravenous injection of 80 mg per kg body weight alloxan on the 4th, 5th, 6th, 7th and 8th days of gestation respectively (the 4th-, 5th-, 6th-, 7th- and 8th-day groups). All mice were weighed on the 1st and 19th days of gestation, and blood sugar levels were tested 48 hours following the alloxan injection and on the 19th day of pregnancy. Pregnant mice were sacrificed on the 19th day of gestation, and fetuses were removed immediately by laparotomy and examined for externally visible defects. The fetal skeleton was examined for deformities after being stained with a dilute aqueous alizarin red-S solution. The frequency of mothers with one or more malformed fetuses was about 30 percent of successful pregnancies, and that of malformed fetuses was about 5 percent of live-borns in each group. The occurrence of fetuses having defects of the central nervous system decreased progressively with later treatments of alloxan during the period from the 4th to 8th days of gestation, and it was presumed that the defects might no longer appear with the alloxan injection after the 10th day of gestation. Hereupon, any noticeable relationship was not particularly seen between the frequency of over-all deformities and the date of alloxan treatment. No appreciable difference in blood sugar levels was observed between mice with and without malformed fetuses. On the other hand, however, fetal defects were found more frequently in mothers with a subnormal increase of the body weight as compared with mothers showing a sufficient increase during the period of pregnancy.
