1. Guinea-pigs on a low, controlled intake of ascorbic acid (0.3 mg/100 g body-weight) were given daily an oral supplement of L-ascorbic acid (AA) or of D-isoascorbic acid (isoAA) (both 1.5 mg/100 g body-weight). The AA was deposited in the tissues, the isoAA was not.

2. Intramuscularly administered isoAA was deposited in the tissues but not to the same extent as equivalent amounts of intramuscularly administered AA.

3. Paper chromatography confirmed that intramuscularly administered isoAA was deposited in the tissues as isoAA, i.e. there was no conversion into AA.

4. It is concluded that in guinea-pigs (a)AA is absorbed from the gastro-intestinal tract much more readily than isoAA and (b)AA is either more readily abstracted from the blood or is more readily retained by the tissues or both, than is isoAA.

1. Lambs fitted with cannulas in the abomasum, terminal ileum and caecum were used to study the digestion of starch and dry matter when rations with high starch content were given. Polyethylene glycol was used as an indigestible reference substance.

2. In Expt I reduction in level of feeding from an estimated ad lib. intake to 70% of this level reduced the amount of dietary starch escaping fermentation in the rumen from 6.8 to 4.4% of intake on a barley diet and from 12.8 to 7.7% on a diet consisting of 40% dried grass and 60 yo barley. Inclusion of 40% chopped dried grass in the diet increased the amount of dietary starch escaping fermentation in the rumen. There appeared to be a linear relationship between the concentrations of starch in abornasal and ilcal dry matter, indicating a limited capacity for starch digestion in the small intestine.

3. In Expt 2 a barley diet was compared with diets based on flaked maize, ground maize or cracked maize. With these diets the percentage of dietary starch escaping fermentation in the rumen was respectively 6.2, 5.4, 12.1 and 142, showing that more starch escapes fermentation with uncooked maize diets than with barley diets.

4. The molar proportions of volatile fatty acids produced by fermentation in the caecum were apparently influenced by the amount of starch passing to the intestines. The highest proportion of acetic acid (78%) was associated with 4.5% of starch in abomasal dry matter, and the lowest proportion (57%)was associated with 20.1% of starch in abomasal dry matter.

5. The possible relationships between the extent of fermentation in the rumen and energy and nitrogen metabolism are discussed.

1. [24-14C]cholic acid was given to conventional and germ-free rats and the faecal isotope excretion studied for 8 days. The turnover, pool size and daily excretion of cholic acid and its metabolites were calculated for rats on three different diets, i.e. a commercial type diet (pellets), a semi-synthetic diet without (D7) and with 20% cellulose (D7+cellulose). The transit time of the intestinal contents was evaluated by following the excretion of an orally administered dose of carmine.

2. The amount of bile acids excreted was two to three times higher in both conventional and germ-free rats receiving pellets than in those receiving diet D7. This difference in bile acid excretion between animals receiving different diets cannot, therefore, be caused by an influence of the diet on the gastro-intestinal microflora. This effect of the commercial diet could not be due to a high fibre content, since an increase in the fibre content of the semi-synthetic diet D7 by the addition of 20% cellulose did not reproduce the effect obtained with the commercial diet.

3. The difference observed in bile acid excretion between germ-free and conventional rats on diet D7 was mainly ascribed to the much longer transit time of intestinal contents in germ-free as compared with conventional rats.

1. One feeding experiment was carried out with seven adult rams (49–65 kg) and a second with eight young rams (39–51 kg) to compare the influence of starch supplementation on the utilization of protein; soya-bean meal was the main protein source in all diets. Cottonseed hulls and Rhodes hay served as energy sources in the basal diets. The energy content of the experimental groups (four adult or four young rams) was increased to 150% of that of the control groups by addition of crushed maize while the intake of digestible protein was equalized by adding maize gluten to control diets.

2. Adult rams retained 20% more nitrogen and young rams 20% less nitrogen on the highenergy than on the control diet. The effect in young rams was not significant.

3. Addition of maize to the diets was followed by a decrease in protein digestibility, but no parallel trend was found between protein digestibility and efficiency of nitrogen retention.

4. In both experiments rumen ammonia and blood urea values were higher in sheep given the control diet than in those receiving the diet supplemented with maize.

5. The dehydrogenase activity of rumen contents from young rams was only slightly raised by the maize supplement compared with the much larger increase that occurred in adult rams.

6. The concentrations of total volatile fatty acids in the rumen contents of adult and young rams were not markedly influenced by the addition of maize to their diets but a slight increase in the concentrations of propionic and butyric acids and a decrease of the ratio of acetic to propionic acid occurred.

1. Serum amino acid ratios and urinary hydroxyproline indices have been studied in three groups of children from different parts of Uganda. The results of these biochemical investigations are compared with clinical assessments and anthropometric measurements made at the same time.

2. In Buganda, an area where protein deficiency is prevalent, a high incidence of both abnormal hydroxyproline indices and amino acid ratios was found. In Karamoja, where a drought had caused a widespread shortage of food, the hydroxyproline indices were particularly low but the amino acid ratios were relatively normal. In Bukedi the dietary pattern was changing and becoming more like that in Buganda; this was reflected by the biochemical results obtained which were similar in the two areas.

3. The biochemical results confirmed earlier investigations, carried out in more severely ill children in a metabolic ward, which had indicated that these two tests can differentiate between primary protein deficiency and total calorie deficiency.

4. The biochemical tests confirmed the anthropometric measurements in a quantitative way, and also indicated the reason for the nutritional difficulties which could otherwise only have been surmised from the food habits of the area.

1. In an experiment of 3 x 3 latin square design, four lactating Holstein cows were given a basal ration designed to induce low percentages of milk fat. The treatments were (I) basal ration, a pelleted mixture of lucerne hay (20%) and concentrates (80%), with 40 l. of water infused intraruminally, (2) basal ration with acetic acid substituted for 15.4% of the metabolizable energy (ME) and (3) propionic acid substituted for 15.4% of the ME. In the last 3 weeks of the 6-week experimental period respiration trials were carried out in an open-circuit indirect calorimeter. The levels of feeding offered in the three periods were 325, 275 and 225 kcal ME/kg body-weight 0.75 in periods 1, 2 and 3 respectively.

2. No differences were detected in the utilization of the energy of acetic and propionic acids, but there were differences in the partition of energy into milk or body tissues; with acetic acid infusion more energy was secreted as milk and with propionic acid infusion more was deposited in body tissue.

3. There was an increase in milk fat percentage with acetic acid infusion, but not complete recovery to normal. The milk fat percentages were 1.96, 2.58 and 1.92 for treatments 1, 2 and 3 respectively. Acetic acid infusion caused increases in the C12, C14 and C16 fatty acids of milk fat and decreased the proportion of C18:1 fatty acids.

4. It is suggested that the low percentages of milk fat found when cows are given concen- trates could result from a decreased extent of fermentation in the rumen, allowing a greater proportion of the starch consumed to be absorbed as glucose in the small intestine.

1. Diets based on ragi (Eleusine corucum) (1) were supplemented with L-lysine monohydrochloride (2) to provide 0.50 g additional lysine per day, or with lucerne leaf protein (3) to provide the same amount of lysine as 2, or with sesame flour (4) to provide the same amount of protein as 3. The effects of such supplementation on the growth and nutritional status of twenty children fed on each diet were studied in a feeding trial lasting for 6 months. Nitrogen retention and apparent digestibility of the diets were also studied at one stage during the feeding trials.

2. Supplementing ragi diets with any of the materials brought about improvement in all nutritional responses, i.e. height, weight, general nutritional status, apparent digestibility and N retention. The diet supplemented with leaf protein led to the greatest response in growth, as measured by increase in height and weight, followed by those supplemented with lysine and sesame flour in that order.

3. The apparent digestibility of the lysine-supplemented diet was lower than those of the diets supplemented with leaf protein and sesame flour.

4. The differences in N retention between the children on the three supplemented diets were not significant.

5. The most important observations were that, although lysine as a sole supplement improved the quality of ragi diets, the leaf protein was superior to it because it improved the quality and increased the content of protein in the diet, and that the sesame flour, in spite of increasing the protein content, did not provide adequate lysine.

1. A description of the population resident on Tristan da Cunha during the winter of 1966 is given.

2. Sources of food supplies are discussed.

3. A brief description of island meal patterns is given and methods of food preparation are discussed.

4. Samples of unusual foods and unique dishes consumed on Tristan da Cunha were collected and analysed for moisture, total nitrogen, fat, calcium, iron and ascorbic acid.

5. The dietary patterns and way of life of the Islanders resident on Tristan da Cunha have changed owing to contact with the outside world and to the development of a monetary economy. These changes were accelerated by the enforced period of 2 years spent in England. The Islanders are now very dependent upon a cash economy and subsistence agriculture provides only a relatively small part of the present diet.

1. Adult rats were trained to consume the entire day's ration in 2 h. They showed marked difference in food intake when a diet lacking in protein was given. Two broad stages were observed, the first phase did not show any drop in calorie intake whereas the second showed distinct severe calorie deficiency.

2. Definite changes were noted in the metabolic profiles of the protein-deficient group even though no evidence for a fall in calorie intake (stage 1) was provided by the measurements of body and organ weights, urinary end-products, liver constituents and liver enzymes.

3. The levels of urinary end-products and liver DNA and RNA decreased in the proteindeficient and pair-fed control groups compared with the control group.

4. The liver glycogen content remained unchanged in the protein-deficient groups whereas the lipid content and the ratio of vitamin A alcohol to ester increased significantly.

5. The activity of xanthine oxidase in the liver was reduced by 75% in the pair-fed control group and by 95% in the protein-deficient group when compared with the control group. However, the activity of succinic dehydrogenase varied, depending on the unit of activity used to express it.

1. The use of chromic oxide (Cr2O3) as an indigestible marker for studies on intestinal digestion in sheep has been examined. The sheep used were equipped with a cannula into the rumen and a re-entrant cannula in the proximal duodenum; some also had a re-entrant cannula in the terminal ileum. The marker was administered twice daily in the form of Cr2O3-impregnated paper, through the rumen cannula.

2. Recovery of Cr2O3 in the faeces, based on 7-day collection periods, was satisfactory, the mean recovery for all seven experiments being 99.6 ± 0.7%. In seventeen 24 h collections of digesta entering the proximal duodenum, the mean recovery of the daily dose of marker was 83.7% (range 63.6-148.4%); in eleven such collections at the terminal ileum the mean recovery was 77.3% (54.0-90.0%).

3. Detailed examination of the concentrations of Cr2O3 in dry matter was made with individual samples taken during single 24 h periods for five duodenal and three ileal collection periods. There were always marked variations in these concentrations. It is concluded that use of short collection periods to give mean values for the flow of digesta throughout the 24 h, at particular points along the tract, may lead to large errors.

1. In four feeding experiments with sheep the utilization of proteins contained in lucerne hay and of those in toasted soya-bean meal (SBM), representing a roughage and concentrate feed respectively, were examined. The ration of one group of animals contained lucerne hay as sole source of digestible protein and that of the other SBM.

2. Measurements of the nitrogen balance showed clearly the superiority of lucerne hay as protein source compared with soya-bean meal; this arose from the greater N retention found with the lucerne hay ration.

3. The influence of both rations on the metabolic pathways of the proteins was examined by following the changes of concentration of various metabolites in the rumen contents and of blood urea at different intervals after feeding.

4. Concentrations of urea found in the blood of the sheep given lucerne hay were lower than those of the other group, a finding which is in agreement with the results of the balance experiments.

5. The concentrations of NH2-N and of aminoacids in the rumen liquor were higher in sheep given lucerne hay than in those given SBM. These concentrations appeared to be related to the differences between the soluble non-protein N contents of the two feeds.

6. The results agree with the finding from in vitro experiments that rumen liquor from sheep receiving lucerne hay promoted greater synthesis of protein than rumen liquor from sheep receiving SBM.

7. Total bacterial activity as measured by the reduction of triphenyltetrazolium chloride (dehydrogenase activity) was much higher in the rumen liquor of sheep given lucerne hay than when SBM was given.

8. The concentrations of volatile fatty acids (C2-C6) were much higher in the rumen liquor in sheep on the lucerne hay diet than in those on the SBM diet. After meals of the lucerne hay diet, the concentrations of acids higher than C2, particularly those of valeric acid, exceeded those present in the rumen liquor of the animals kept on the SBM diet.

9. Proline and alanine appeared in relatively higher concentrations in the rumen liquor than the other amino acids determined, and these two acids together with valine disappeared very rapidly. The possible conversion of these amino acids into valeric acid is considered. It is suggested that valeric acid found in relatively high concentrations in rumen liquor of sheep given lucerne hay may be due in part to the deamination of proline, which likewise disappeared very rapidly together with alanine and valine.

1. Individual energy intakes and expenditures of seven Tristan men aged between 16 and 57 years, and ten Tristan women aged between 15 and 61 years, were measured daily for 7 consecutive days between May and October 1966.

2. Details of the subjects' main activities together with the energy cost of these activities are given.

3. The mean daily calorie intakes were 2650 kcal for men and 1830 kcal for women; the mean expenditures were 2860 and 2060 kcal per day respectively. Separate values are given for two individuals, a brother and sister, who gave results bearing no resemblance to those of the rest of the subjects.

4. Protein, fat, carbohydrate and alcohol accounted for 12.7, 29.6, 53.7 and 40 % respectively of the men's total calorie intake and 11.9, 27.2, 61.0% and 0% of the women's total calorie intake. The fat content of the diet was low when compared with that of the Islanders' diet while in England, though total calorie intake was greater (Taylor, Hollingsworth & Chambers, 1966). More than half the total calorie intake was provided by processed foodstuffs, but island produce provided a large proportion of the protein in the diet.

5. It is deduced that mean energy requirements of about 2750 kcal per day for men and 1950 kcal per day for women are adequate for the Tristan population and that there are sufficient food supplies available to meet this requirement.

1. The feeding of a protein-free diet to adult rats trained to consume their whole day's food in 2 h changed the characteristics of hepatic lysosomes immediately upon the onset of protein deficiency combined with calorie deficiency.

2. The nature of the alterations in the characteristics of liver lysosomes were deduced from the faster release of enzymes, swelling of membranes and a change in the sedimenting properties. Purified lysosomes from pooled livers from a group of rats fed on a protein-free diet for only a day, showed marked differences when compared with lysosomes from normal rats. When lysosomes were suspended in sucrose solutions of two different molar concentrations, the release of acid phosphatase occurred at a faster rate in liver lysosomes of protein-starved rats than in those of normal ones. The light-scattering characteristics of the suspensions suggested the presence of swollen lysosomes in livers of rats fed on a protein-free diet and normal lysosomes in the livers of control rats.

3. In homogenate of liver from rats fed on a protein-free diet for 11 days the levels of cathepsin and acid ribonuclease showed a five- to six-fold increase in the free specific activities when compared with those of controls.

4. The role of lysosomes is discussed with reference to the accumulation of hydrolytic endproducts and liver autolysis during protein starvation.

1. The behaviour of fatty acids in dilute bile salt solution and in dispersions of triglyceride in bile salt solution was examined. The properties of fatty acids in bile salt solution were defined in terms of their saturation ratio, and of the critical micellar concentration of bile salt for each fatty acid as solute. The partition of fatty acids between the oil phase and the micellar phase of the dispersions was defined as the distribution coefficient K M/O. The phases were separated by ultracentrifugation.

2. Of the fatty acids examined, palmitic and stearic acids behaved in bile salt solution as typical non-polar solutes. Lauric, oleic and linoleic acids had properties similar to typical amphiphiles. The effectiveness of these and other amphiphiles was expressed in terms of an amphiphilic index.

3. The trans-fatty acids, vaccenic acid and linolelaidic acid possessed solubility properties similar to their cis-isomers. The properties of elaidic acid were intermediate between those of the non-polar and the amphiphilic solutes.

4. The distribution coefficients of fatty acids differed less significantly than their solubilities in bile salt solution, but were influenced to some extent by the composition of the oil phase.

5. The effect of pH on the partition of fatty acids was similar for all fatty acids examined. There was a marked increase in the partition of fatty acids in the micellar phase as pH increased above 6.2.

6. In the presence of Ca2+ ions above a threshold concentration of I m-equiv./l. and at a pH higher than 6.4, the partition of stearic acid in the micellar phase of the bi-phasic system was restricted. No interaction of Ca2+ ion and pH was observed with oleic acid.

7. The effect of some amphiphiles on the distribution coefficient of stearic acid was examined. The capacity of lysolecithin to solubilize stearic acid in the micellar phase of dispersions was about twice that of I-mono-olein. The significance of the results in relation to fat absorption in the pig and the sheep is discussed.

1. Male and female chickens were reared from hatching on vitamin A-free diets, either unsupplemented or containing retinoic acid (vitamin A acid), methyl retinoate or retinyl acetate (vitamin A acetate). The birds given retinyl acetate grew well and had a normal appearance, but those given the unsupplemented diet died before 4 weeks of age after developing typical signs of avitaminosis A. The birds given retinoic acid or methyl retinoate did not show overt signs of vitamin A deficiency or other abnormalities except for a progressive failure of vision. Minimal histological changes were found in their retinas, and their vision was rapidly restored after feeding with retinyl acetate.

2. The cocks maintained with retinoic acid or methyl retinoate had normal testes and the hens laid eggs at a normal rate, but although their eggs could be obtained fertile the development of the embryo became abnormal after 2 days incubation and it always died. The development of the embryos could be stimulated and sometimes restored to normal by injection of various forms of vitamin A into the eggs before incubation, or by previous administration of retinyl acetate to the hens.

3. It is concluded that feeding retinoic acid as the sole source of vitamin A enables the hen to produce eggs that lack vitamin A but are otherwise normal, thus permitting the demonstration of a hitherto undescribed requirement of the early chick embryo for vitamin A.

4. The toxicity of vitamin A derivatives to chick embryos was investigated; injected retinoic acid was found to be extremely toxic.

1. The interrelationship between cholesterol and vitamin A metabolism has been studied in rats.

2. The effect of cholesterol feeding in increasing the liver storage of cholesterol w-as enhanced during vitamin A deficiency.

3. This effect was due to an increased rate of absorption of cholesterol and not due to a decreased turnover rate.

4. Feeding of high levels of vitamin A markedly depressed the cholesterol absorption; however, its turnover was unaffected.