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Summary and conclusionsPregnant women receiving daily supplements of 400 IU (10 ,tg) of vitamin D2 from the 12th week of pregnancy had plasma calcium concentrations higher at 24 weeks but similar at delivery to those in control pregnant women who did not receive the supplements. Infants of the women receiving the supplements had higher calcium, lower phosphorus, and similar magnesium concentrations on the sixth day of life and a lower incidence of hypocalcaemia than infants of the control women. Plasma concentrations of 25-hydroxycholecalciferol, which showed a seasonal variation, were higher in mothers and infants in the treated group. Cord-blood calcium, magnesium, phosphorus, and 25-hydroxycholecalciferol concentrations correlated with maternal values at delivery. Breast-fed infants had higher calcium and magnesium and lower phosphorus and 25-hydroxycholecalciferol concentrations than artificially fed infants. A defect of dental enamel was found in a high proportion of infants (many of whom had suffered from hypocalcaemia) born to the control women.These results suggest that vitamin D supplementation during pregnancy would be beneficial for mothers, whose intake from diet and skin synthesis is appreciably less than 500 IU of vitamin D daily.

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There are numerous studies of goal-directed behavior which demonstrate that although an animal's approach (or avoidance) responses are reinforced at but a limited region in space, and in the presence of restricted patterns of stimulation, similar responses will also be evoked in adjoining regions and by other patterns of stimulation. Usually, it is observed that when magnitude of response is plotted against distance from the region of reinforcement, a gradient is formed; response magnitude decreasing with distance.Of the several hypotheses which have been advanced to account for these and attendant facts, Hull's ( 14) goal-gradient hypothesis is perhaps the most satisfactory. It can be shown, however, that a number of these facts are also in accord with the concept of the spatial generalization of conditioned responses. 2 * Starting time is defined as the time required for a rat to run from the starting point to the center of the runway, a distance of 30 cm.