Summary Negro groups in West, Central and Southern Africa, also in Jamaica, have mean cardio-thoracic ratios significantly greater than those in corresponding age-sex groups of Caucasians. To throw more light on the situation, studies on young and elderly Negroes have been made in certain groups in Southern Africa, also on local Caucasian groups. Only slight differences in ratio were found between local Negro groups, and Caucasian groups in South Africa, also in Wales and Tecumseh (U.S.A.). Yet ratios in Negro males from Malawi and Mozambique, resident in South Africa, were significantly greater than values in local Negroes. High ratios are not therefore invariable for Negroes. The difference observed relates to heart, not thoracic diameter. Since the phenomenon, which concerns heart position, is apparent in the young, almost certainly it is of ethnic origin. Investigations on cardiomegaly in African populations must take this factor into reckoning. Its presence or absence locally may readily be assessed by determining ratios in relatively small numbers of young people of both sexes.

Most primitive and emerging populations obtain their calcium, largely or almost wholly, from vegetable sources. Of these, edible leaves (wild and cultivated), in certain contexts, are very important. To throw light on the availability of the calcium content, five common types of cooked edible leaves or "spinaches", all having low concentrations of oxalic acid, were fed in amounts containing about 200 mg calcium, to groups of South African Negro children. Urinary calcium excretions, accruing over 6 hour periods, were determined. The mean amounts of calcium excreted were of the same order and similar to that resulting from consumption of a volume of milk containing 200 mg calcium. Using the methodology described, it was confirmed that the calcium in Swiss Chard "spinach", (Spinacia oleracea) with its high oxalic acid content, is poorly absorbed. Nevertheless, it is inferred that the calcium contained in leaves of "spinaches" commonly consumed is available for utilization, a finding in agreement with observations on South African Negroes with respect to the satisfactory composition, dimensions, and other related indices of bone which reflect calcium status.

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