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The amount present in the liver must be very small, however, and it is evident that the main tendency is for azobenzene to be rapidly eliminated as the water-soluble hydrazo derivative. Azobenzene is not carcinogenic, but in work which is being carried out with the carcinogenic p-dimethylamino-azobenzene evidence has been obtained that similar metabolic changes take place. In this case, however, the hydrazo derivative dbes not appear to be so stable and undergoes the benzidine rearrangement in the body more readily, since a substance giving the colour reaction of one of the 'benzidine change' products of p-dimethylamino-azobenzene can be extracted directly from the neutral or alkaline urine.

The opinion is widely held that oatmeal may have a detrimental effect upon Ca absorption because of its high content of phytate-P. The only investigation undertaken specifically to study this effect in man is-that of Burton (1929-30), who compared absorptions and retentions of Ca and P in children and adults receiving wheat and oatmeal diets. This worker found better retentions of Ca when wheat diets were taken. The children were irradiated with ultraviolet light, and in four cases out of six the Ca absorptions and retentions were several times the normal values established by Duckworth & Warnock (1942). Further, the Ca intake was not equalized, so that in all subjects but one the Ca intake was greater on the wheat than on the oatmeal diet. Steggerda & Mitchell (1939), who incidentally used a basal diet rich in oatmeal to keep the Ca intake low, found Ca absorption and requirement within normal ranges. Since McCance & Widdowson (1935, 1942) found that, under their experimental conditions, adult man excreted approximately half the ingested phytate-P of wheaten flour and that the phytates seriously interfered with the absorption of dietary calcium, it appeared desirable to investigate the utilization of phytate-P in oatmeal at various levels of Ca intake. At the same time it was thought desirable to follow the balances of Ca and Fe. METHODS The general pattern of the diet was made to conform, as far as possible under the conditions of the experiment, with that found by Cathcart, Murray & Beveridge (1940) to prevail in the Scottish Highlands. To keep the Ca content of the diet low, cheese was eliminated and milk intake reduced. Since the oatmeal intake in the Highlands is lower today than hitherto, the allowance was increased to bring it closer to that consumed during last century (Hutchison, 1868). This led to a corresponding reduction in flour intake. To simplify the experimental procedure, to reduce the amount of analysis, and to minimize the variability of factors other than Ca intake, a constant diet was eaten throughout the study. This was made possible by the collaboration of the Low Temperature Research Station and the Torry Research Station, both of the Department of Scientific and Industrial Research, to whom our thanks are due for generous gifts of dehydrated foodstuffs and frozen fish.

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