1. Biscuits baked to a recipe requiring only sucrose, white flour and water were ground to a powder and mixed with the remaining ingredients of a standard rat diet. The control diet contained the same dry-weight amounts of all ingredients, but the sucrose and flour were not baked into biscuits. Eighty-four rats were divided into two matched groups and fed on the diets for 8 weeks from weaning.

2. The biscuit diet produced significantly more caries than the control diet, with a total of about twice as many lesions, and also many more advanced lesions. Nearly all the lesions were in the molar fissures, suggesting that the cooked and powdered biscuit was impacted and retained in the fissures.

1. A combination of balance and isotope techniques has been used to study the effects of dietary supplements of NH4Cl, given for 1 and 10 weeks, on calcium metabolism in 1- and 2-year-old wethers.

2. The main effects of the NH4C1 supplements were to decrease urinary pH, increase urinary Ca excretion and to increase Ca absorption and the percentage of dietary Ca absorbed.

3. The results were different from those obtained by other workers in man and rat, and possible explanations of this difference are discussed.

4. A difference was also found between 1- and 2-year-old animals in their long-term response to the NH4Cl supplement. This difference may have been due to a lack of available Ca in the diet of the younger animals, and prolonged ingestion of NH4C1 may increase the amounts of Ca absorbed and retained.

1. The increase in metabolic rate which occurs after ingestion of protein (the so-called ‘specific dynamic action’) has been attributed to the energy requirements for urea synthesis and amino acid degradation.

2. We have tested, in normal adult subjects, the effect of meals which increase or decrease the rate of urea production, and our results do not substantiate this hypothesis.

3. The difficulties of accurate measurement of resting metabolic rate are discussed.

4. The term ‘specific dynamic action’ is inappropriate since the effect is not specific. We believe that it may prove to be a reflection of protein synthesis rather than of protein catabolism.

1. Metabolic balance studies of manganese were made on four young women, using brilliant blue and chromic oxide as faecal markers.

2. Mn concentrations in food, faeces and urine were measured by atomic absorption spectrophotometry.

3. No difference in Mn concentrations was obtained between dry-ashing and wet-digestion for removal of organic matter from food or from faeces.

4. Retentions of 0.05–0.46 mg Mn/d were obtained. Dermal and menstrual losses were not measured or allowed for.

5. Unlike most other Mn balance studies reported, the retentions obtained were consistent with the accepted size and stability of the body pool of Mn in healthy adult subjects.

The manganese concentrations of breast-milk, liquid and dried cow's milk, and foods widely used in mixed feeding of infants in New Zealand, were measured by atomic absorption spectrophotometry.

The dietary supply of Mn to infants during the first 6 months was calculated. This varied from 2.5 to 75 μg/d per kg body-weight depending upon the age of the infant, the type of milk and the quantity of solid foods consumed. Young infants in New Zealand received about as much Mn as has been reported for infants elsewhere.