“…Table 1 shows that concentration of calcium was higher in sera from the mixed arteriovenous blood of the two human foetuses than in the corresponding matemal sera, but the latter were rather low compared with normal values for adults. A depression of maternal serum calcium, especially during the latter half of pregnancy, has been repeatedly described (Bodansky & Duff, 1936;Harding, 1925;de Wesselow, 1922;Ramsay, Thierens &Magee, 1938, andMull, 1936a, b). According to Mull (1936a) the calcium concentration in the foetal serum, although always higher than that in the maternal serum, is determined by the latter.…”