Postnatal developmental changes in forelimb muscle (m. triceps brachii) were studied in dystrophic mice (C57BL/6J dy/dy). At an early age of 2.3 weeks, tissue weight and α-bungarotoxin uptake per unit weight of the muscle were not different between normal and dystrophic mice. With age, the muscle weight increased markedly in normal mice against only a slight increase in dystrophic ones, and the toxin uptake decreased in normal but not almost at all in dystrophic mice. Significant differences between normal and dystrophic mice were observed after 4 and 6 weeks of age as to toxin uptake and muscle weight, respectively. The muscle-body weight ratio was very similar in normal and dystrophic mice and it varied little during the period from 2.3 to 8 weeks of age. Diameter-frequency analysis showed that muscle fibers were much thinner in dystrophic than in nor-mal mice at 12 weeks old. The present findings strongly suggest that in dystrophic mice muscle fibers suffer from a maturational defect in the forelimbs as well.

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Time courses of changes in amplitudes of muscular potentials of gastrocnemius muscles under prolonged sciatic nerve stimulation of 5 per sec were investigated in dystrophic, dwarf and their crossbred mice. In those mice that were classified as dystrophic according to their characteristic features, the amplitudes of muscular potentials changed only slightly, whereas they were depressed to a notable extent in others.

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A case of metaphyseal chondrodysplasia of the Schmid type was reported. The patient was a twenty-two month old girl exhibiting marked metaphyseal roentgenographic irregularities of the joints of the hips, knees, and ankles. Short stature and genu varum were also demonstrated in three consecutive generations of the patient's family.

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The relation of the vasculature to the developing skeletal anlagen in the fetal hamster limb bud was studied with the scanning electron microscope during abnormal development induced by maternal retinoic acid treatment. Blood vessels in limbs from retinoic acid-treated fetuses were found scattered in the limb bud mesenchyme in areas where chondrogenic skeletal condensations normally appear. It is hypothesized that these abnormally placed blood vessels could physically interfere with the process of mesenchymal condensation and contribute to dysmorphogenesis of the skeletal anlagen.

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Since the thalidomide episode, several monitoring systems for birth defects have been developed throughout the world. The International Clearing-house for Birth Defects Monitoring Systems established in 1974 plays an important role in the exchange of information relevant to birth defects and/or monitoring systems. There are two types of monitoring systems, namely, population-based and hospital-based. Though the Tokyo Area Birth Defects Monitoring Program (hospital-based) has participated in the activities of the Clearinghouse, no population-based monitoring systems exist in Japan prior to 1981 . The Kanagawa Birth Defects Monitoring Program has been in operation since October 1981 as the first population-based monitoring system in Japan. In this program, 48 marker malformations and other major surface anomalies are monitored for all births (live births and stillbirths) within 7 days after birth. A guide-book distributed to all participating maternity hospitals plays an extremely important role in increasing the completeness of ascertainment of malformations.

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