Teratogenic and embryocidal effects of methylmercuric chloride were studied in rats and mice. A single oral administration of 35 mg/kg of methylmercuric chloride was given to pregnant Wistar rats on day 6, 8, 10, 12 or 14 of pregnancy. Pregnant ddN mice were orally administered with a single dose of 30 mg/kg on each day from day 6 to 13 of pregnancy. Increase in intrauterine death and fetal growth retardation were marked in most treated groups both in rats and mice. In both of these groups, hydrocephalus was manifest. In mice, a high incidence of cleft palate, micrognathia and microglossia was noted. Brain lesions such as tissue defects and focal necrosis in the brain mantle, corpus callosum, nucleus caudatus-putamen, thalamus, hypothalamus and primordial cerebellum were detected in every treated group of rats and mice.

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1. Fertile eggs were subjected to a clockwise centrifugal force (0.592 × m. gr. force) for a period of 9 hours. 2. Experimental embryos exhibited various anomalies of the heart and great vessels, such as aortic arch anomaly, ventricular septal defect, atrial septal defect, and double outlet right ventricle. In the control group, only ventricular septal defect was found. It was small in size compared to the experimental group. 3. Congenital malformation of the cardiovascular system might be caused by the effect of centrifugal force which induced an alteration of the flow pattern, stagnation or injery to cardiac tissue in the developing cardiac tube. 4. Further investigation will be needed to produce the specific malformation of cardiovascular system by changing gravity of centrifugal force, and selecting specific embryonic stage.

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