1. ‘58Co’cyanocobalamin was given by stomach tube to Wistar albino rats aged between 6 h and 24 days. The fraction of the dose absorbed was assessed by measuring the amount retained by the animals after 7 days, by total body counting.

2. Rats up to 4 days old absorbed about 90% of the test dose, compared with a mean of 83% at the age of 8 days, 66% at 16 days and 47% at 24 days.

3. The proportion of the test dose absorbed did not appear to be affected by starvation for up to 24 h, by increasing the dose from 0·05 ng to 0·25 ng/g body-weight, or by giving the ‘58Co’cyanocobalamin mixed with rat's milk.

4. The results support earlier suggestions that newborn rats absorb vitamin B12 by a different mechanism from that in adults.

1. After a preliminary period of 2 weeks indoor feeding on hay, two groups of wethers grazed either a timothy pasture or a ryegrass-dominant pasture for 12 weeks. The timothy was particularly low in sodium and chlorine.

2. Within a week of turning out, saliva sodium fell and potassium increased in the timothy group, and by the end of the experiment, the sodium: potassium ratio was 1.9:1. The changes in saliva were not reflected in blood composition. The rate of live-weight gain was similar in both groups of sheep.

3. The results confirm those of a previous indoor experiment and show that timothy supplies insufficient sodium to maintain the normal saliva composition of sheep.

1. Details are given of modifications to standard pH measuring equipment enabling it to be used to record continuously the pH in the bovine rumen for up to 4 weeks. The operation of the apparatus and examples of its use are presented.

1. Six healthy young women residing in a metabolic unit, but continuing their normal activities, received a uniform diet for 27 days, subdivided into four periods of 6 days and a final collection period of 3 days.

2. The daily food was divided into equal-sized portions; the subjects ate their daily quota as three meals a day in periods 1, 3, and 5 (control), two meals in period 2 (gorging), and nine meals in period 4 (nibbling).

3. The metabolic response of each subject was investigated by measurements of energy expenditure, and by analysis of the food, the urine and the faeces.

4.The subjects showed distinct differences in response, but for most subjects the changes in body-weight and in the metabolism of nitrogen and fat appeared unrelated to the frequency of the meals.

1. Diets containing various sugar mixtures together with polyethylene glycol of high molecular weight as a marker were fed to pigs 1, 2 and 3 weeks old. The piglets were slaughtered 2.5 h later, and the ratio of sugar to marker was determined in the contents of the alimentary tract as far as the caecum.

2. The greatest fall was found in the first part of the small intestine.

3. Glucose had always disappeared by the third quarter of the small intestine.

4. Xylose and fructose disappeared more slowly, especially in the younger pigs, but were usually absent from the contents of the last quarter of the small intestine.

5. Sucrose was removed far less completely, and the ratio of sucrose to marker frequently did not decrease along the second half of the small intestine. Sucrose was removed much less efficiently when it formed 15% of the diet than when it formed only 5%, and much less efficiently by the younger than by the older pigs.

1. In Expt 1, four adult wether sheep were given diets of hay or dried grass in an alternating sequence of feeding treatments. Each treatment period lasted for 20 days and blood samples were taken from the sheep on the last day of each period. When the diet of hay (linoleic: linolenic acid ratio 1.40) was replaced by one of dried grass (linoleic: linolenic acid ratio 0.28), there was an increase in the concentration of linolenic acid and a decrease in the concentration of linoleic acid in the plasma cholesteryl esters and phospholipids. There was an increase in the concentration of stearic acid and a decrease in the concentration of palmitic acid in the plasma triglycerides. Dietary change did not affect the composition of the plasma unesterified fatty acids.

2. In Expt 2, two adult wether sheep, each with a rumen fistula, were given daily intraruminal infusions of 60 g of ‘linolenic’ or ‘linoleic’ acids (both about 70% pure) over a period of 5 days. The infusion treatments were then reversed. Blood samples were taken at the end of each infusion period. Intraruminal infusions of ‘linolenic’ acid increased the concentration of linolenic acid in the plasma cholesteryl esters and phospholipids and increased the concentration of stearic acid in the plasma triglycerides. The infusions of ‘linoleic’ acid increased the concentration of linoleic acid in the plasma cholesteryl esters and phospholipids. No appreciable changes were observed in the composition of the plasma unesterified fatty acids.

1. Numbers of erupted primary teeth were counted in young children in four rural villages in The Gambia. The ages of all children were precisely known, and their heights and weights were measured.

2. The majority of children were recorded as having an even number of teeth. The number of primary teeth present in children of given age varied widely. Up to 18 months of age, the Gambian children lagged behind American and European children in number of erupted teeth.

3. From the distributions, it appears that a child having no teeth is unlikely to be over 12 months of age, and one with all primary teeth is unlikely to be under 20 months. Between these dental limits, estimates of age from the number of primary teeth present are likely to be accurate to ± 3 or 4 months.

4. Children who were tall or heavy for age tended to have more teeth than those who were short or light. Thus, children with delayed dentition would be systematically assessed as younger than true chronological age.

5. There was, however, no evidence that slow growth was associated with prolongation of the total period of dental eruption, nor that seasonal variations in rate of growth were associated with similar variations in rate of tooth eruption.

1. Thirty-six nitrogen-balance measurements were made on children recovering from malnutrition. Two types of diet were used: a high-protein diet providing from 1·25 to 6·0 g protein/kg per day which supported normal growth, and a low-protein diet providing 0·75 g protein/kg per day on which the children were approximately in N balance. Both diets provided 120 kcal/kg per day.

2. The size of the labile protein pool was estimated from the N lost on changing from a high- to a low-protein diet. After the change of diet a new equilibrium was reached in about 3 days.

3. Labile protein, as defined above, represented about 1·2% of the total body protein on changing from 6·0 to 0·75 g protein/kg per day, and about 0·2% of total body protein on changing from 1·5 to 0·75 g protein/kg per day. The magnitude of the labile protein pool did not appear to be related to the nutritional state of the child.

4. It is concluded that the labile protein pool is not a reservoir which can be filled, but that losses of N which occur on reducing the protein intake of an infant reflect a lag in metabolic adjustment.

1. Polyethylene glycol (PEG) of high molecular weight, used as a dietary marker, did not distribute uniformly in the water present in a high-casein diet as did glucose, a low-molecular-weight substance.

2. This distribution effect also occurred with the contents of the stomach and, to a smaller extent, with the contents of the first quarter of the small intestine of piglets given such a diet.

1. Groups of chicks were given diets containing four levels of vitamins A and D, 1, 10, 100 and 1000 times the basal level, in all sixteen combinations, with the object of investigating a possible antagonism between the two vitamins.

2. Only diets containing 1000 times the basal level (approx. 1700 times the dietary requirements) of one or both vitamins depressed growth and induced changes in the blood.

3. The packed cell volume was substantially reduced from 4 weeks of age in the chicks given the highest level of vitamin A. It is suggested that this was due to an effect of the vitamin on the fragility of the red cells and thus on their life span.

4. Chicks given the toxic level of vitamin D showed an increase in plasma calcium and a decrease in plasma inorganic phosphorus. The highest level of vitamin A depressed plasma Ca without influencing plasma inorganic P. Increasing amounts of vitamin A given in combination with the highest level of vitamin D caused a progressive increase in the plasma inorganic P.

5. The highest level of dietary vitamin A significantly increased the activity in the plasma of three lysosomal enzymes: acid phosphatase, β-glucuronidase and arylsulphatase. Excess vitamin D given in conjunction with the basal level of vitamin A significantly depressed the plasma acid phosphatase and the activity of this enzyme increased with increasing amounts of vitamin A. Excess vitamin D had no influence on the other hydrolases studied.

6. A marked antagonism between the effects of excessive amounts of the two vitamins occurred only in respect of their actions on the plasma levels of Ca, inorganic P and acid phosphatase, all of which are involved in bone metabolism.

1. Germ-free (GF) and conventional (CV) rabbits wearing collars to prevent coprophagy were fed an autoclaved diet with added cellulose. Their faecal excretion was analysed to determine nutrient digestibility.

2. Clearly distinguishable hard faeces were excreted by the GF rabbit only if the diet contained at least 15% cellulose. Unlike CV rabbits, the GF rabbits did not consume their soft faeces even when permitted to do so. Soft faeces made up a larger proportion of the total output of GF than of CV rabbits. Food intake and total dry-matter excretion per kg body-weight were similar in both groups.

3. Although digestibility of dry matter was similar in the two groups, in the GF rabbits there was a higher digestibility of crude fat and true protein and a lower digestibility of crude fibre and nitrogen-free extract. GF rabbits excreted a higher percentage of ingested calcium and phosphorus in the urine than did CV rabbits.

4. The results suggest that intestinal microbes, even without the enhancing effect of coprophagy, aid in the digestion of carbohydrate by rabbits. The greater faecal excretion of crude fat and true protein by CV rabbits could result from poorer digestion and absorption, but could also represent nutrients synthesized by microbes from simpler materials. The reingestion of faecal crude fat and true protein might therefore improve the quality of the total nutrient intake. The results suggest ways of assuring an adequate dietary intake by GF rabbits in the absence of contributions from an intestinal microflora.