1. Fifty-six albino rats were distributed between four dietary groups in fourteen randomized blocks of four animals. Each block consisted of siblings and each member of the block received a different dietary treatment. 2. The diets permitted normal growth and the only variations were: group I contained 67% sucrose, group 2 an equivalent amount of uncooked maize starch and groups 3 and 467 % of finely ground Thin Wine and Morning Coffee biscuits respectively. 3. After 31 days on the diet, the animals were killed and assessed for dental caries. The rats of group I had significantly more caries than the other groups. The rats of group 2 had significantly less caries than the other groups. The biscuit diets produced significantly less caries than the sucrose diet, but significantly more caries than the starch diet.

1. Assessment of sugar intake by our short questionnaire has been shown to agree well with its assessment by the conventional method in which subjects keep a 7-day diary of their diets. 2. People who have had a myocardial infarct, or are suffering from peripheral vascular disease, tend to reduce their intake of sugar. We believe this is the reason why investigators making dietary studies several months, or years, after infarction have not found the relatively high sugar consumption in patients with infarction that we had reported earlier. 3. The most suitable method for ascertaining dietary intake depends both on the constituent or constituents to be examined, and on the purpose of the investigation.

1. After feeding radioactive markers 85Sr and 45Ca for 10 days to weanling and adult rats receiving basal diets all of which contained adequate calcium and phosphorus to support normal growth, the skeletal retention of the markers was compared with that in litter-mates receiving seven different P compounds as dietary supplements so that the P intake was increased 2 to 3½ times. 2. In weanling rats a dietary supplement of KH2PO4 decreased the skeletal retention of 85Sr by some 30% without affecting the retention of 46Ca. In adults on this supplement, the skeletal retention of 85Sr was reduced by over 40% compared with controls on the same basal diet. 3. When the supplement contained Ca as well as P the reduction in skeletal retention of 85Sr in young and adult rats was greater than when no Ca was present in the supplement. 4. It is concluded that there was no experimental evidence to show that supplements of P which also contained Ca induced any Ca deficiency in the rats. 5. In rats receiving P supplements which also contained Ca, the ratio of the skeletal retention of 85Sr, experimental to controls, was 0.45 for weanling rats and 0.52 in adults, 34 weeks old. These ratios were not significantly different for any of the seven supplements used. 6. From comparisons with previous experiments, it is concluded that supplementation with Ca plus P is more promising as a remedial measure for decreasing the uptake of radioactive Sr from the diet than supplementation with Ca alone.

1. Susceptibility to dietary induction of hypercholesterolaemia and aortic atherosis was compared in two groups of male New Zealand White rabbits. 2. Twelve rabbits were purchased from one breeding establishment (group I) and twelve from another (group 2). On arrival at the laboratory six animals from each group were killed and the aortas were removed. Blood samples were taken from the remaining twelve animals and then they were given ad lib. for a period of 40 weeks an atherogenic diet containing 20% butterfat. During this period food intake and body-weight were recorded. At the end of the period blood samples were taken from the animals and immediately afterwards they were killed and the aortas were removed. 3. No atheromatous lesions were found in the aortas of the rabbits in either group killed at the beginning of the experiment. There were no differences between the two groups of animals with respect to body-weight or concentration of cholesterol in the plasma at the beginning of the experiment, food intake during the experiment or body-weight at the end of the experiment. At the end of the experiment, the degree of aortic atherosis in the rabbits of group I was considerably greater than that in the rabbits of group 2. 4. At the end of the experiment the concentrations of total lipids, free cholesterol, esterified cholesterol and phospholipids in the plasma of the rabbits in group 1 were significantly higher than the corresponding concentrations of these lipid components in the plasma of the rabbits in group 2. The concentrations of palmitic, stearic and linoleic acids in the cholesterol esters and the concentration of palmitic acid in the unesterified fatty acids in the plasma of the rabbits in group 2 were significantly higher than the corresponding concentrations of these fatty acids in the plasma cholesterol esters and unesterified fatty acids in the rabbits of group 1. 5. It is concluded that these differences in response to the atherogenic diet were reflections of the differences in the susceptibilities to the dietary induction of hypercholesterolaemia and atherosis of the two differents strain of rabbit that had been established by the two commercial breeders. Such differences in susceptibility could readily explain certain discrepancies in the results of various research workers engaged in this field of investigation.

1. Methionine-deficient diets were given to rats for 4 weeks. 2. This resulted in a decrease in total body iron, due to a decrease either in Fe absorption or Fe retention. 3. There was inhibition of growth, development of anaemia and a shift of body Fe to the liver. 4. There were no histological alterations which could be interpreted as specific to methionine deficiency. 5. These findings were different from reports of effects of ethionine in which there is an increased Fe absorption and various tissue alterations, including pancreatic acinar and liver damage.

1. Loss of NH3 N from faeces and urine between voiding and collection and also losses in expired air, eructed gas and from the skin of wether sheep 2–3 years old given a ration of 400, 700, 1000 or 1300 g dried grass/day have been measured. 2. Losses of NH3 from faeces were negligible, and the loss from urine depended on the temperature and pH at which it was collected. Collection at neutral pH resulted in losses of up to 9.7% of the urinary N as NH3 gas if an acid trap were not incorporated in the collection apparatus. The average loss of N on collection of urine at pH values below 2.0 was 1.33% when the ambient temperature was between 25 and 28°, and 0.97% when it was between 15 and 18°. 3. Very little NH3 was lost in expired air or eructed gas, but when total NH3 loss other than that from urine was determined, an average loss of 3.14±0.55 mg N/kg body-weight per day was found. This loss was independent of food intake and larger than the loss of N in suint which was estimated to range from 0.59 to 2.55 mg N/kg body-weight per day with the rations given. It was concluded that the larger losses found in some experiments were due to splashing of urine on to the fleece during collection and subsequent loss of this urine N as NH3. It was shown that the losses of NH3 N due to errors in urine collection and failure to consider dermal losses ranged between 1.2 and 2.6% of the total determined losses in faeces and urine for sheep fed on a variety of diets and that the losses varied inversely with intake of N.

1. The confusion sometimes found in discussions of dietary vitamin A and its precursors is illustrated. The relative potency of vitamin A and carotene is briefly discussed, and the procedure used in the National Food Survey of Great Britain explained. 2. Changes in the vitamin A and carotene contents of the British diet over the last two decades are illustrated. 3. The vitamin A and carotene contents of the American diet are estimated, and compared with those of the British diets; both estimates of intake are compared with recommended allowances. The difficulties of making such comparisons are discussed, in view of the different conventions used in the two countries. 4. An appendix, on the calculation of vitamin A in the diet, is included, in which interrelations between different methods of expressing vitamin A value are shown.

1. For 26 weeks, adult male rats were fed on diets containing about 80 % of carbohydrate, given as dextrose, fructose, liquid glucose, or sucrose; their performance was compared with that of rats receiving a standard laboratory cubed diet (41 B) containing 60 % of carbohydrate, mainly as starch. 2. More of diet 41 B was eaten than of any of the diets containing sugars, but only with dextrose was the mean body-weight gain significantly lower than with diet 41 B. 3. No significant differences in body length or girth were produced by the different diets. 4. Compared with those of rats given diet 41B, plasma cholesterol levels were significantly in- creased by fructose and sucrose and to a lesser extent by dextrose, but not by liquid glucose. 5. Compared with those given diet 41 B, the rats given fructose had heavier hearts, kidneys and livers, those given sucrose had heavier hearts and livers, and those given dextrose had heavier hearts. Those given fructose had the heaviest kidneys and livers, and heavier hearts than those given liquid glucose. The organ weights of those given liquid glucose and those given diet 41 B were not significantly different. 6. Compared with the values on diet 41B, carcass and liver fat were both significantly increased by sucrose and fructose but not by dex- trose or liquid glucose. With fructose, liver fat was almost double that with dextrose or liquid glucose. 7. Dry-matter contents of whole carcass and liver followed substantially the same pattern as did the fat contents. 8. Liver protein content was significantly lower on the 80 % carbohydrate diets. The reductions were greatest with fructose and sucrose.

1. Beef fat (2.5%) and anchovy oil (2.5%; 2.5% plus 0.02% ethoxyquin; 5%) were incorporated into isocaloric cereal-based diets A, B, C and D and given to turkeys from 2 to 10 weeks of age. Diets A, B, and C contained 13 and diet D 26 i.u. α-tocopheryl acetate/kg. The lipids of diets B and D, which contained fish oil without ethoxyquin, autoxidized in the feeding troughs, but not seriously in the brief period of exposure permitted. 2. The birds all remained healthy and grew well, the only nutritional effects of the fish oil being a depressed storage of vitamin A in the liver at both levels of feeding (prevented by ethoxyquin) and a slightly adverse effect, at the higher level only, on food conversion ratio. 3. The skin fats of the birds given fish oil contained seven major and two minor fatty acids, derived from the fish oil, which were not present in the skin of the control group given beef fat, as well as one major fish oil acid present in much greater concentration in the birds given fish oil than in the controls. All these acids were present in the skin fats at about half or two-thirds of their concentrations in the dietary lipid, except for acid 22:5, which reached two or three times this level. 4. The stabilities towards autoxidation of the skin fats decreased in the order A > C > B > D, as their content of polyunsaturated fatty acids increased, but the greater stability of group C as compared with B was probably due, in the main, to the higher tocopherol content of the skin fat of the birds on the ethoxyquin-containing diet. Fishy flavours which developed on cooking showed a similar relationship to diet.

1. Coprophagy in rats was prevented by the use of a leather jacket and large-mesh, screen floor cages. 2. This caused considerable depression of growth of prevented rats compared with non-prevented rats on the same diet.

1. Nine experiments, each with one of six sheep with cannulated rumens given a constant diet of dried grass, were made in which oleic, linoleic or linolenic acid was infused into the rumen and energy and lipid metabolism were measured. One experiment was made in which palmitic acid was given. 2. Judged by changes in the composition of isolated fatty acids, the unsaturated fatty acids were hydrogenated in the rumen. An increase in the excretion of lipid in the faeces occurred when the unsaturated acids were given. The heat of combustion of the faeces increased by 12.6±3.0 kcal/100 kcal fatty acid, of which 94% was accounted for by the additional lipid. 3. Methane production fell when the unsaturated fatty acids were infused, the decreases being 13.8±1.6 kcal CH4;/I00 kcal oleic acid, 14.2±1.5 kcal CH4/100 kcal linoIeic acid and 16.4±1.3 kcal CH4/100 kcal Iinolenic acid. The introduction of a double bond into an n-alkyl acid was calculated to reduce methane production by 0.24±0.09 moles/mole double bond. 4. Because the depression of methane production on infusing the fatty acids exceeded the increase in the heat of combustion of the faeces, the metabolizable energy of the fatty acids was 104.1±5.3% of their heat of combustion. 5. The efficiencies with which the fatty acids were used to promote energy retention were 74.6±5.7% for oleic acid, 79.2±2.0 % for linoleic acid and 82.5±3.0% for linolenic acid. These efficiencies agreed with those noted in experiments by others with rats, horses and pigs given glycerides, but were higher than those noted by others when glycerides were added to the diets of ruminants.

1. The blood sugar, lactate and pyruvate levels of sixty-nine Ugandan children, during treatment for kwashiorkor, have been studied. 2. The majority of untreated cases had low levels of blood glucose but high levels of lactate and pyruvate. Children with the lowest glucose levels had the lowest serum protein values and gained weight more slowly. 3. The response of the blood glucose to glucagon or adrenaline was twice as great at the end of treatment as at the beginning. 4. In children whose treatment was successful the lactate and pyruvate levels gradually fell to the normal range. There was a rise in the blood glucose value but after 3 weeks the level was still below that found in normal African children. In a few children who died or whose treatment was complicated by pyrexia and general apathy there was a rapid fall in lactate and pyruvate concentration to abnormally low levels.

1. The intake and excretion of energy, total nitrogen, fat and carbohydrate by twenty baby boys aged about a fortnight were measured over 3 days. 2. Ten of the babies received breast milk which had been expressed from their mothers, the remaining ten received one of two preparations based on dried cow's milk, with either lactose or sucrose added. 3. The intake of energy, protein and carbohydrate was greater in the ten babies receiving the cow's milk preparations. 4. The urinary excretion and retention of N was greater in the babies fed on the cow's milk preparations. 5. The absolute excretion of N in the faeces was simiIar whatever the diet, but the excretion of fat was less and the excretion of carbohydrate greater for babies having breast milk. 6. The calorie:N ratio in the urine was 5.8 kcal/g urinary N in those receiving breast milk and 4.8 kcal/g N in those fed on the cow's milk preparations. The value for the adult is 7.9. 7. Calorie conversion factors have been calculated which are more appropriate for milk diets for babies than the factors of Atwater which were designed for mixed diets for adults.

1. Two sheep were given cubed rations in which the fatty acid content was increased by about 12 g/day at the end of each week, until the daily intake became 74 g. 2. The apparent digestibility of the crude lipid increased with the increased intake, but there was no tendency for the digestibility of the fatty acids to increase or decrease regularly. 3. Comparison of faecal losses during the final periods, when a maximum amount of lipid was given, with the losses during the initial control periods showed that the excretion of dry matter, crude lipid and cellulose increased. The excretion of crude protein was unchanged and that of lipid- and cellulose-free dry matter decreased. There was a reduction in the production of methane of 17 kcal/100 kcal of additional fatty acids in the diet. 4. The concentration of the C18 unsaturated acids in the rumen liquor reached a maximum during the 1st week on the diet containing the maximum amount of added fatty acids. The shape of the curves was consistent with rapid hydrogenation of linolenic acid. The concentration of stearic acid in the rumen liquor reached a maximum when the dietary acids increased to only 50% of their maximum value.

1. The dietary intakes of forty-one mothers were investigated during lactation, between the 6th and 20th weeks after delivery. The group comprised thirty primiparae and eleven multiparae. 2. The women studied were apparently lactating satisfactorily, as the infants were judged healthy and their average weekly weight gain was 193 g (6.9 OZ). 3. The average daily intakes of nutrients by the mothers were compared to those listed in Dietary Allowances for Australia. Intakes of calories, protein, calcium, iron and ascorbic acid were 514±75 (16%), 17.0±2.7 g(17%), 725±75 mg(36%), 5.2±0.43 mg (31%) and 21±5.3 mg (21%) respectively below the allowances for these nutrients. It is suggested that the allowances for calories, protein, calcium, iron and ascorbic acid may have been set at too high a level. 4. The incidence of successful breast-feeding in western countries compared with others is briefly discussed. It is concluded that diet plays a minor part and that the dominant factors are cultural and social.

1. Portions of a preparation of freeze-dried cod fillet were subjected to different conditions of heat treatment and were then digested in vitro with pronase (an enzyme preparation from Streptomyces griseus), or successively with pepsin, pancreatin and erepsin, or with pepsin and papain. The digestions were conducted under ‘static’ conditions in flasks, and also in Sephadex gel G 10 in such a manner that the reaction products were continuously removed from the site of action of the digesting enzymes. The different digests were then passed in turn through a calibrated column of Sephadex gel G25 and each was resolved into three fractions containing ‘soluble protein’, ‘peptide’ and ‘free amino acids’. The distribution of several amino acids in these different fractions was determined and the results were assessed in relation to the availabilities of these amino acids in the original test proteins as measured in microbiological and chemical tests and, in some instances, in growth tests with rats. 2. The different enzyme systems gave broadly similar results. With increasing severity of heating, the ‘ free amino acids’ component in the digests became increasingly deficient in several amino acids relative to their content in the original unheated meal, and notably in lysine and the sulphur-containing amino acids. This evidence for a marked differential effect of heating in retarding the enzymic release in vitro of several amino acids was consistent with the results of feeding tests with rats, and of microbiological and chemical assays, which showed corresponding differences in the proportions of lysine, methionine and isoleucine made unavailable by the heat treatment. In severely heated meal more of the lysine, methionine and isoleucine was released by enzymes in vitro than was biologically available to the rat. With increasing severity of heat treatment, the biological availabilities of these amino acids for the rat fell more sharply than did the digestibility of the nitrogen, indicating that amino acids absorbed from the heated meals were relatively poorly retained.

1. The food and water intake and diurnal variations in the rumen contents were measured in sheep with rumen fistulas receiving semi-purified or pelleted roughage-concentrate diets. The rates of secretion and composition of parotid saliva of the sheep on both diets and of sheep fed on hay were determined. The sheep had continuous access to the diet. 2. The mean daily intakes of the semi-purified and roughage-concentrate diets were 920 and 2234 g respectively. The corresponding water intakes were 2.50 and 6.05 1.3. Noneof the sheep ruminated on either diet. The weight of total contents and of dry matter in the rumen was highest in animals on the roughage-concentrate diet, and marked diurnal fluctuations, which reflect the eating habits of these animals, were observed. The semi-purified diet appeared to have a very marked water-retaining capacity in the rumen. 4. The estimated daily total secretion of both parotid glands was 2.7, 5.4 and 11.5 1. in sheep fed on the semi-purified diet, roughage-concentrate and hay respectively. No appreciable differences were observed in the composition of parotid saliva between the three groups of sheep. In sheep receiving hay, saliva secretion was lower during eating than between periods of eating, during part of which time the sheep presumably ruminated. 5. It is concluded that the observed differences in parotid secretion reflected differences in the physical form of the diet.

1. In Expt 1 balance studies were carried out with six wether sheep receiving chopped hay and concentrates and given, 0, 5, or 101. water/day by intraruminal infusion. Allocation to two 3 x 3 latin squares was arranged to allow calculation of main treatment and residual effects.

2. Infusing 101.water/day increased the total daily urinary output of magnesium, phosphorus and sodium by 31, 45 and 100% (P<0.05). Faecal losses of Mg, and P tended to decrease correspondingly and with both elements retention remained positive but retention of Na became negative (P < 0.05). 3. Residual effects were not detected, and infusing 5 1. water/ day generally produced intermediate and non-significant effects. 4. When pellets made from dried, ground, young spring pasture or ccncentrates rich in Mg were included in the diet of four wethers in Expts 2 and 3, infusions of 101. water/day produced much greater decrcases in faecal losses and retentions of Na and K and greater increases in the urinary excretion of those elements than those found in Expt I. Effects on Mg, P and Ca balance were similar to those in the main experiment. 5. The biological significance of these results and relationships between the observed effects and the aetiology of hypomagnesaemic tetany are discussed.

1. A series of trials has been conducted to investigate interactions between amino acids in the diet of the growing chick. 2. Diets were prepared in which the level of arginine was limiting. To these diets were added excess levels of lysine, histidine, isoleucine and leucine. Of these amino acids lysine was most effective in reducing the growth rate. Growth rate was restored by adding arginine. 3. The addition of excess quantities of lysine to a diet in which the level of tryptophan was limiting and the level of arginine adequate did not reduce growth rate. 4. These results confirm the existence of a specific interaction between arginine and lysine. The concept is discussed that such specific interactions between pairs or among small groups of amino acids might underly many of the phenomenons of amino acid imbalance.