The time and order of appearance of the ossification centers of the skull, the axial skeleton, the appendicular skeleton, and the pectoral and pelvic girdles were studied in fetuses of the golden hamster. They were cleared with KOH and stained with alizarin red S by Dawson's method. The results obtained were as follows.
1. The first appearance of an ossification center in all the skeletons is in the clavicle at 11 days and 15 hours post coitus. 2. In the axial skeletons, the first ossification center appears in the cervical vertebral arches at 12 days and 15 hours. The vertebral bodies ossify at 13 days and 12 hours in the thoracic bodies somewhat later than the respective vertebral arches. 3. The anterior appendages begin to ossify a few hours earlier than the posterior ones. 4. The first ossification center in the skull appears in the mandible at 12 days. Before the time of birth all the skull bones except for the ethmoid begin to ossify. 5. The ossification of newborn hamsters seems immature when compared to those of the rat and the mouse in which more ossification centers are present at birth than in the hamster, especially in the manus and pes.

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The blood volume (TBV) of four inbred strains of mice with different hemoglobin types, single and diffuse, were estimated by the method for Evans blue dilution. TBV of AA and SS strains with single type hemoglobin, was 12.2ml/100g body weight, and the value in C3H/He and CF#1 strains with diffuse type hemoglobin was 10.8ml/100g body weight. The differences between the two estimated values were highly significant (P<.001) . However, they were not statistically different between AA and SS strains, and between C3H/He and, CF#1 strains. It was suggested that there were hematological compensation in the traits of hemoglobin content, red cell count and TBV, because hemoglobin content and red cell count in mice with diffuse type were larger than those of mice with single type, and the opposite relationship in TBV was present.

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An inbred strain, ACI/N rat, was imported at the 82nd generation from the National Institute of Health, U.S.A. and the sister-brother mating of the rats has been continued in our laboratory. The rats were fed with a commercial chow, CE-2 (CLEA Japan Inc.) and bred in an air-conditioned room (24±1°C, 55% humidity) . Increase of body weight, diet uptake, malformation, and reproductive potential were examined during the breeding. In order to know the homogeneity of the rats, transplantability of 3 strains of syngeneic ascites hepatomas into the rats was also examined. Increase of body weight of male and female rats reached to plateau 80 days and 60 days after birth, and average weight at the 90th day was 234g and 164g, respectively. Body weight of the rats was relatively lower than that of Donryu and Wistar-Imamichi rat of the same age. Average daily diet-uptake of 50-day-old ACI/N rats was 15 g per rat. Rates of fertilization, deliverling, and nursing in ACI/N rats were relatively better than those in the other two strains of rats. However, mean litter size was 5.6 and it was smaller than that of the other two strains of rats. Abnormality of kidney, which was lack or hydronephorosis of one kidney, was observed in 16% male and 10% female ACI/N rats. Transplantation of 10⁶ascites hepatoma cells syngeneic to ACI/N rats killed 100% of the host by either intraperitoneal, intravenous, or subcutaneous injection.

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In 14 pregnant cynomolgus monkeys, red blood cell count, hematocrit value, hemoglobin content, white blood cell count and serum total protein content were determined during the period from the time of mating to the 8th postpartum week, and in other 12 pregnant and 9 nonpregnant females of the same species, erythrocyte sedimention rate, serum specific gravity, serum transaminase activity and serum total cholesterol level were measured during the same period as that of the former group. Slight anemia and sharp elevation of erythrocyte sedimentation rate were observed in the last 4 weeks of gestation period. The decrease of white blood cell count, serum total protein content, serum specific gravity and serum total cholesterol level became noticeable after the first half period of gestation until parturition. No remarkable change of the value of serum transaminase activity was observed throughout the gestation period. These changes of blood properties observed in the pregnant monkeys disappeared within 8 weeks after delivery. These monkey showed no clinical disorder throughout the experimental period, and all of them delivered apparently healthy baby monkeys. Therefore, the hematological changes observed can be regarded as the physiological phenomena associating with the course of normal pregnancy.

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A new type of nozzle for drinking water supply to mice was devised. The main advantageous characteristics of the devised nozzle when compared with the nozzle used ordinarily are as follows; 1) The stress of elastic gum is used as the pressure of valve, by which the power pressing valve became much stable (Figs. 1 vs. 2) . 2) Unnecessary passive withdrawal of water through push bar much decreased. 3) The structure is very simple and is suitable for mass production (Figs. 1 vs. 2) . 4) The power for drinking water is small (within 5 g) (Fig. 9) and drinking is very easy even in young mice. Employing this type of nozzle, the growth, reproduction, amounts of water and food consumed were quite normal (Figs. 10, 11 and 12) . The devised nozzle is applicable to the feeding of mice in an isolator as well as in a cage with wood shavings.

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