1. Four groups of weanling rats were maintained on diets containing either 0.12% or 0.24% of both calcium and phosphorus, in the presence and absence of added ergocalciferol. 2. Increase in mineral intake or the provision of vitamin D increased the final body-weight, with a significant interaction between the two factors. 3. Serum Ca and P concentrations were raised significantly by both the vitamin and the increase in mineral intake without signi ficant interaction. 4. Measurements were made of bone and tooth weights and ash values and of the length of the humeri. For only two measurements was there any interaction between the effect of vitamin D and increase in mineral intake, namely the length of the humeri, and their ash values expressed as a percentage of the dry fat-free weight. 5. It is concluded that in relation to the amount of mineral deposited, the incisor tooth is more resistant to nutritional stress than is the bone.

1. In ileal contents from differently fed ruminating calves, examined under conditions approximating to those obtaining in vivo, 34–74% of the magnesium and 63–93% of the calcium were non-ultrafilterable. The binding was shown to be due to at least two processes, one depending on the presence of phosphate, the other not. 2. Considerable non-phosphate binding occurred in samples adjusted in vitro to pH 5.5 and above. The binding material was probably not a single substance but the bound forms of both Mg and Ca were, at least partly, in equilibrium with the soluble forms, and some competition between the two metals occurred. Thus in any one sample the extent of binding for either metal was influenced by the concentration of both. With normal concentrations it was estimated that, in the ileum, about one-third of the Mg and half of the Ca was bound in this way, irrespective of whether pasture or one of a variety of stall diets was given. 3. Samples adjusted to about pH 6.5 and above (in vivo ileum pH was about 7.4–7.9) showed further precipitation of Ca and Mg to an extent which partly depended on the concentration of inorganic phosphate. Ca precipitation appeared to be mainly controlled by the concentration of Ca and inorganic phosphate but for Mg the precipitation depended also on the presence of factors other than Mg and inorganic phosphate. One such factor found to be present was the ammonium ion, but its practical importance is uncertain. 4. Ileal contents from milk-fed calves showed considerable non-phosphate binding of Ca but not of Mg.

1. Body water content was estimated in sixteen pigs at each of three weights 27, 55 and 90 kg with tritium, 4-aminoantipyrene (4-AA) and N-acetyl-4-aminoantipyrene (NAAP). The values obtained were compared with chemical analysis of the whole carcass. 2. The tritium method estimated total body water content accurately at 27 kg live weight but overestimated it by approximately 10% at both 55 and 90 kg live weight. 3. Antipyrene was eliminated from the pig at a rate of 55%/h and could not be used for body water estimations. 4. Measurements with NAAP on nine pigs tended slightly to underestimate total body water content. Estimates with 4-AA showed no association with the values obtained by chemical analysis.

1. Twenty-four Ayrshire bull calves were reared on either high-concentrate or high-roughage diets to study the effect of diet on the subsequent ability of the calf to digest either concentrates or hay when given alone. The rearing diets were known to produce different types of rumen development. 2. Although there were significant differences between the apparent digestibility coefficients of the high-concentrate and high-roughage rearing diets and between concentrates and hay when given alone, the subsequent ability of the calf to digest either concentrates or hay was unaffected by the type of diet given during the rearing period to 13 weeks of age. 3. The amount of nitrogen retained was significantly greater in calves reared on the high-concentrate diet than in those given the high-roughage diet, but similar amounts of N were retained/100 g gain in body-weight in both groups. After the change in diet, the amount of N retained was significantly greater in calves given concentrates after a rearing diet high in concentrates than in those given concentrates after a rearing diet high in roughage, although in both groups 32% of the N intake was retained. Four of the six calves given hay after a rearing diet high in concentrates were in negative N balance, but only one calf lost weight. Only 19% of the N intake was retained in calves given hay after being reared on a high-roughage diet. 4. The concentration of total volatile fatty acids (VFA) in the rumen contents rose to reach peak levels at about 3 h after food was offered; the concentration then declined. VFA concentrations tended to be higher in calves given the rearing diet high in concentrates than in those given the one high in roughage, and differences reached significance when the diet was changed to one of all concentrates or all hay, with no obvious carry-over effect of the rearing diet. The proportion of propionic, butyric and higher acids tended to be greater in calves given high levels of concentrates than in those given high levels of hay and also tended to rise, irrespective of diet, as the concentration of total VFA rose. 5. A change of diet at 14 weeks from one high in concentrates to one consisting entirely of hay resulted in a significant decline in the viable counts of streptococci, lactobacilli and coliform organisms in the rumen liquor at 16 weeks. The numbers of bacteria were unaffected by the other dietary changes. 6. The concentration of total VFA in plasma of peripheral blood tended to be higher in calves given the high-roughage or all-hay diets. A fall in the concentration of plasma VFA occurred when calves were changed from a high-roughage diet to an all-concentrate diet and a rise in concentration was observed when an all-hay diet replaced one containing a high proportion of concentrates. 7. During the initial rearing period the mean blood plasma glucose concentration was 92.8 mg/100 ml in calves given the high-concentrate diet, a value significantly higher than the mean value of 64.5 mg/100 ml found in calves given the high-roughage diet. The concentra- tion of plasma glucose rose to 89.8 mg/100 ml in calves changed from the high-roughage diet to concentrates and declined to 81.7 mg/100 ml in calves that were given hay in place of the high-concentrate diet. 8. The weight of contents of the reticulo-nunen and omasum and the volume displacement of these organs were significantly greater in calves given hay as the sole diet during the last 3 weeks of life than in those given concentrates during this period. The weight of tissue forming the reticulo-rumen was significantly greater in calves given the all- concentrate diet during the last 3 weeks of life than in those given only hay during this period. It was apparent that the rumen papillas developed rapidly in those calves given concentrates as the sole diet for a period of 3 weeks after a rearing diet high in roughage, whereas there was a marked retrogression of papillas when concentrates were withdrawn from the diet. 9. It is concluded that the ruminant calf adapts readily to marked dietary changes, with the result that differences in the size and structure of the ruminant stomach, which have been shown to occur when different types of diet are given, have no permanent effect on the ability of the calf to digest diets of concentrates or hay.

1. Prolonged intermittent exposure to reduced environmental temperature (+2°) produced in rats given a nutritionally well-balanced diet a decrease in the concentration of esterified fatty acids in the blood serum, liver and epididymal fat tissue. In the last there was a significant increase in the unesterified: esterified fatty acid ratio. The hepatic synthesis of fatty acids from [1–14C]acetate remained unchanged. A decrease in the concentration of cholesterol was found in the blood serum, liver and lungs of animals exposed to cold.

2. When a high-fat, high-cholesterol diet was given, exposure to cold increased the mobilization of lipids; this was indicated by the elevation of the unesterified fatty acid levels in the blood serum and in the epididymal fat tissue. In rats given the high-fat diet the lipotropic action of cold on the liver was confirmed. This action was characterized by a decrease of esterified fatty acid levels and by an increase of glycogen concentration in the liver. This effect is probably due to a lowering of hepatic lipogenesis and to increased oxidation of fatty acids in the liver tissue. In rats given the high-fat dict, cold exposure produced an increased cholesterol accumulation in the tissues and more pronounced morphological changes in the myocardium.

1. The results of over 500 determinations of the heat of combustion of the urine produced by cattle and sheep have been analysed statistically. 2. The analytical errors for nitrogen, carbon and heat of combustion were ±0.54, ±1.4 and ±2.2%. The error attached to an estimate of the heat of combustion of the urine produced by an individual sheep in 4 days was ± 10%.3. At the maintenance level of feeding, the heat of combustion of the urine (U kcal/ 100 kcal food) was related to the crude protein content of the diet (P%)by the equation

U = 0.25P+1.6

with a residual standard deviation of ±0.88 kcal/100 kcal.4. Regression analysis of the relation between the heat of combustion of urine and its N content showed significant differences with diet. The heat of combustion of the urine of sheep was 9.7 kcal/g C and of cattle 10.3 kcal/g C, and did not vary with diet. 5. It is shown that the variation in the heat of combustion of urine/g N and its relative constancy/g C arises largely from variation, from diet to diet, in the proportion of the N excreted as hippurate. 6. The results have been combined with the results of a similar analysis (Blaxter & Clapperton, 1965) of methane production by sheep to show that the ratio of metabolizable energy to digested energy varies very little from mean values of 0.82 for roughages, 0.85 for cereals and 0.79 for oilseed cakes and meals.

1. Subcutaneous fat thickness has been measured by three different techniques in forty-one subjects. 2. Ultrasound provided the most accurate measurement in experienced hands. 3. A method based on electrical conductivity was also accurate but was unpleasant for the subject. 4. Harpenden calipers were the least satisfactory of the three techniques tested.

1. The effect of reducing the hay and of increasing the proportions of concentrate and flaked maize in the diet of cows on the secretion of milk fat and its component fatty acids and on the proportions of volatile fatty acids in the rumen liquor has been studied. 2. The low-hay diet caused a fall in the milk fat content to about half of the values in the initial control period and the secretion of all the major fatty acids in the milk was reduced. The general pattern of change in the proportions of rumen VFA during the change to the low-hay diet was a decrease in acetic acid, an increase in propionic and n-valeric acids, relatively little change in n-butyric acid and also an increase in the concentration of lactic acid. Approximately 60% of the variation in milk fat content during the change of diet was associated with the increase in propionic acid. 3. In cows established on the low-hay diet there were marked variations in the relative proportions of acetic and propionic acids, but there was no related change in milk fat content. On return of the animals to the high-hay diet, recovery of the initial proportions of acetic, propionic and valeric acids occurred within about 4 days but the recovery in milk fat content was not complete until 2–3 weeks had elapsed. 4. Although the intraruminal infusion of acetic acid in cows on the low-hay diet caused increases and decreases respectively in the molar proportions of acetic and propionic acids in the rumen, an increase in milk fat content was observed amounting to only one-quarter of the loss associated with the transfer to the low-hay diet; therem was no characteristic pattern of increase in the yields of the individual fatty acids of milk fat. No consistent effects of intraruminal infusions of butyric acid, in cows on the low-hay diet, on the yield of milk fat or of the individual fatty acids were observed.

1. Rats were chronically depleted of protein by being kept on a 6% casein diet for 5–8 weeks. Control rats were fed on a normal diet. Both groups were injected intraperitoneally with L-[U-14C]lysine. Some rats from each group were then put on a protein-free diet to produce acute depletion. The animals were killed 3 days after the injection. 2. The organs and tissues were analysed for total nitrogen and radioactivity. Free lysine, total amino N and specific activity of free lysine were measured in muscle, liver and serum. The total muscle mass of the animals was determined. Samples of muscle and skin were fractionated and the sp. ac. of the fractions was measured. 3. The main loss of N in acute depletion was found in the viscera and carcass residue; the percentage of total body N contributed by muscle was increased in protein-depleted rats. 4. The depleted rats retained relatively more radioactivity in the internal organs and less in the carcass than normal rats. 5. The ratio of the sp. ac. in protein-bound lysine to the sp. ac. of free lysine showed that protein synthesis was reduced in the muscle of the protein-depleted rats, although there was no decrease in the amount or sp. ac. of free lysine even in severe depletion. 6. Sarcoplasmic and fibrillar proteins of muscle were equally affected by protein depletion, but there was some indication of a preferential decrease in protein synthesis in one of the skin fractions. 7. The results for muscle protein are compared with those given in the literature for liver proteins. It is suggested that the rat adapts to a low-protein intake by an alteration in the pattern of protein synthesis.

1. A combination of balance and isotope techniques was used to determine the influence of phosphorus depletion on the size of the exchangeable calcium pool and on the rates of Ca deposition in and removal from the whole skeleton of sheep. 2. The exchangeable Ca pool was reduced in size in the depleted sheep to approximately 50% of that in the controls. 3. The rates of Ca deposition in and removal from bone were reduced by P depletion and the rate of Ca transfer from the pool was reduced slightly. 4. The turnover rates of the exchangeable Ca pool and bone Ca in sheep appear to be similar to values published for man.

1. A comparison of the distribution of radioactivity in rat tissue lipids after oral administra- tion of [5-Me-14C]-α-tocopherol showed that spleen and adrenal lipids have a relatively high uptake of radioactivity. 2. Absorbed α-tocopherol and its metabolites appeared not to re-enter the lumen of the gut in significant amount through the bile or by the secretion from the stomach mucosal cells within the 24 h experimental period. 3. After ingestion of [5-Me-14C]-α-tocopherol by rats, analyses of their liver and spleen lipids showed that most of the radioactivity in the lipids was due to the presence of unchanged α-tocopherol. Radioactive tocopherolquinone was found in both spleen and liver lipids; in the liver lipids there was some evidence that a second oxidation product of α-tocopherol, compound O, had been formed.

1. Two experiments were conducted to examine the effect of grinding and pelleting roughages on the voluntary intake of food, digestibility, time of retention of food in the digestive tract, amounts of digesta in the recitulo-rumen and eating and ruminating behaviour of adult, non-lactating, non-pregnant cows. The first experiment was with artificially dried grass and the second with oat straw; also, with a diet of ground, pelleted oat straw the effect was studied of giving a daily intraruminal infusion of 150 g urea. The size of the particles of the ground roughages are given. 2. The mean voluntary intakes of long and ground dried grass were similar, the voluntary intake of ground, pelleted oat straw was 26% greater than that of long straw and the daily infusion of urea increased the voluntary intake of ground, pelleted oat straw by 53%. 3. The digestibility of the ground roughages was lower than that of the long roughages, the lower digestibility of the ground roughages was due mainly to the poor digestibility of crude fibre in the reticulo-rumen. The rate of disappearance of cotton thread placed in the ventral sac of the rumen was slower with ground than with long roughages. 4. The mean times of retention of ground roughages were shorter than those of long roughages when equal and restricted amounts of each food were given; with food offered ad lib. there was little difference between the mean times of retention of long and ground roughages in the alimentary tract. 5. On average, the mean amounts of digesta dry matter in the reticulo-rumen immediately after a meal were about the same with long and ground dried grass, with long and ground oat straw the amounts of dry matter were similar, but when the intraruminal infusion of urea was given the amount of dry matter increased by 49%. 6. The rate of eating (min/kg food) ground, pelleted roughages was much faster than that with long roughages; when the cows received ground roughage rumination did not occur but during short periods triple reticular contractions were seen. 7. The relationship between the voluntary intake of food, the amount of digesta in the reticulo-rumen and the rate of disappearance of digesta from the alimentary tract is discussed.

1. Groups of male rabbits (ten to thirteen per group survived) were given ad lib. a diet consisting of 80 parts of a low-fat basal diet to which were added: for group I, 20 parts maize oil; for group 2, 20 parts butterfat; for group 3, 10parts maize oil and and 10parts butter- fat; for group 4, 0.47 parts maize oil and 43.1 parts wheat starch; and for group 5, 10.2parts maize oil and 21.6 parts wheat starch. The animals in group 6 were givenan ordinary com- mercial rabbit diet. 2. The rabbits were given the various diets for 38 weeks, after which a sample of blood was taken. The rabbits were then killed and the liver and a sample of perine- phric adipose tissue were removed from each animal. The plasma, liver and adipose tissue lipids werefractionated on columns of Florisil and the fatty acid compositions of the tri- glyceride and unesterified fatty acid fractions were determined by gas-liquid chromatography.

3. The effects of the different diets on the composition of the unesterifiedfatty acids in the plasma were very similar to the effects of the diets on the fatty acid composition of the plasma triglycerides, but in the plasma unesterified fatty acids the concentration of stearic acid was consistently higher and the concentration of linoleic acid was consistently lower than in the plasma triglycerides. 4. There appeared to be a positive rectilinear relationship between the concentration of stearic acid in the plasma triglycerides and the concentration of triglycerides in the plasma. 5. In the triglycerides of the plasma, the concentrations of palmitic and stearic acids were consistently greater and the concentration of linoleic acid was consistently less than the corresponding concentrations of these fatty acids in the triglycerides of the adipose tissues. In the two groups of rabbits given low-fat diets the fatty acid composition of the liver trigly- cerides was almost identical with that of the plasma triglycerides. 6. In each of the six groups of rabbits the composition of the unesterified fatty acids in the plasma was identical with that of the unesterified fatty acids in the adipose tissues. Inthe unesterified fatty acids of the liver the concentrations of linoleic andarachidonic acids were consistently greater and the concentrations of myristic, palmitic and palmitoleic acids were consistently less than the corresponding concentrations of these acids in the unesterified fatty acids of the plasma and adipose tissues. 7. The results of this investigation are discussedin the light of recent con-cepts on the metabolic relationships between the unesterified fatty acids and triglycerides of the liver, plasma and adipose tissues.

1. Lipids of the heart muscle, skeletal muscle and liver were investigated in healthy calves and in calves suffering from enzootic muscular dystrophy with special regard to the fatty acid composition of the phospholipids and triglycerides. 2. Healthy young calves and older calves differed in the fatty acid composition of these tissues. The tissue phospholipids of healthy young calves contained less linoleic acid and more monounsaturated fatty acids than those of older calves. Of the saturated fatty acids, palmitic acid content tended to be higher in young calves and stearic acid content tended to be higher in older calves. 3. The stearic acid content of tissue triglycerides was lower in young calves than in older calves. 4. Fatty aldehydes were present in the phospholipid fraction of the heart muscle and of the skeletal muscle. Stearaldehyde content was higher in older calves than in young calves. 5. In calves with muscular dystrophy definite changes in the fatty acid composition of the phospholipids were found. In young calves the content of linoleic acid was higher and that of monounsaturated fatty acids lower in tissues of diseased animals than in the corresponding tissues of healthy controls. Both in young and older calves arachidonic acid content was higher in the degenerated areas of the skeletal muscle than in the healthy controls. 6. Possible relationships between the tocopherol and arachidonic acid contents of the tissues are discussed. 7. In the triglyceride fraction the differences between diseased and healthy tissues were less significant than in the phospholipid fraction in young calves. In older calves no significant differences were found. 8. An increase in lipid content was found in the degenerated areas of the skeletal muscle and a decrease in livers from diseased animals. An increase in free cholesterol was found in the degenerated areas of the skeletal muscle. The triglyceride content of livers from diseased animals was decreased. The relative proportion of phospholipids was less in skeletal muscle and higher in liver of diseased animals than in the corresponding tissues of healthy controls.

1. Rats were maintained from the age of 3 weeks until the end of a second reproductive cycle on diets having different protein values and Ca concentrations. 2. Reproductive performance was judged from the number of viable young, their size, body composition and rate of growth during suckling. 3. The size and quality of the bones of the mothers and offspring were assessed from radiographs, histological appearance, total weight of ash, ash/cm3 and ash:organic matter ratios of dry fat-free bone. 4. At the end of gestation the mean numbers and total weights of foetuses were low when the mothers had received diets of low protein value: there were smaller differences in the body-weight, water, ash and N contents of the individual foetuses. 5. When 0.44% Ca was included in the diet of low protein value, only one (three rats) of the six litters born survived beyond 1 week of age. 6. At weaning, the young born of and suckled by the protein-calorie deficient dams were only about half the weight of those from mothers receiving the high-protein diets; Ca deficiency produced relatively minor changes. 7. All the mothers lost weight during lactation irrespective of the protein value or Ca concentration of the diet; their bones had lower radiographic densities and less ash/cm3 than is usual in non-pregnant rats of similar age. 8. The interaction of protein and Ca and their relative importance in maintaining the skeletal structure of mother and offspring during pregnancy and lactation are discussed.

1. Three sheep were given three diets, a control diet consisting mainly of cereals, a similar diet incorporating linseed oil (mainly glycerides of linolenic acid) and a diet incorporating free fatty acids derived from linseed oil. The diets were given at the maintenance level and at twice this level according to a latin square design. 2. Complete energy balance was obtained and the digestibilities of cellulose and lipid were determined with each sheep receiving each diet. The relative amounts of various fatty acids in the dietary and faecal lipids were also estimated. 3. The inclusion of lipids in the diet resulted in a significant decrease in cellulose digestion, whereas the lipid digestibility increased. 4. The proportion of C18 acids increased in the faeces, and the proportion of bacterial fatty acids decreased, but since the total amount of fatty acids excreted increased, the amount of bacterial fatty acids excreted per day did not differ significantly in animals receiving the control diet and the diets containing added lipids. 5. The addition of lipids to the diet resulted in a highly significant drop in methane production, the depression being about 25% of the control value. The depression (28.9 kcal/100 kcal of fatty acids given) was considerably greater than the depression produced by continuous infusion of the same amount of fatty acids. 6. Because of the depression of CH4 production and of some reduction in the urinary energy losses, the addition of lipids to the basal diet increased the metabolizable energy by about 9.5 kcal/100 g of the basal diet. 7. The efficiencies of utilization of metabolizable energy were not significantly affected by addition of lipids, being about 82% for maintenance and 62% for fattening. 8. In an experiment with one sheep, comparison was made between the effect of slow continous infusion of fatty acids over 24 h and the effect of rapid infusion of the same amount twice daily during feeding. The continuous infusion of linseed oil fatty acids resulted in a drop in CH4 production of 16.3 kcal/100 kcal of fatty acids given. This was in good agreement with previous findings. Rapid infusion of these fatty acids resulted in a drop in CH, production, amounting to 28.0 kcal/100 kcal of fatty acids infused. This is comparable with the reduction of 28.9 kcal/100 kcal fatty acids when the fatty acids were incorporated in the diet.

1. A comparative study has been made of five methods of saponifying normal and vitamin E-deficient rat liver and subsequently measuring ubiquinone and α-tocopherol. 2. Losses of ubiquinone and α-tocopherol occur under certain conditions, and three of the methods were judged to be unsatisfactory. Recoveries of α-tocopherol are nearly quantitative under the conditions of ToŠić & Moore (1945), but methods that use large reaction times or weaker alkali destroy tocopherol, and over 50 % loss can be encountered. Ubiquinone does not seem as sensitive to the time of reaction, but is sensitive to the concentration of alkali and amount of water present during saponification.

1. Measurements were made of the proteases, amylase and lipase of the pancreas and of the corresponding intestinal, caecal and colonic contents of germ-free and conventional rats. 2. Little difference was found between the concentration of the enzymes in the germ-free and conventional rats. 3. The results indicate that intestinal bacteria had only a minor part in determining the fate of the pancreatic enzymes in the contents of the intestine, caecum and colon. 4. The enzyme concentrations decreased caudally. The proteases were the most stable, and the amylase was the least stable; the stability of lipase was intermediate between that of the proteases and amylase. 5. Evidence of bacterial activity in the caecal contents of conventional rats was seen in the greater percentage of protein nitrogen and in the lower percentage of the non-protein nitrogen

1. Sixteen experiments were made with eight sheep to determine the effects of various compounds on methane production, digestion and metabolism. 2. Two experiments with two sheep given stearic acid incorporated in the diet showed that it depressed CH4 production by 2.7 moles/mole stearic acid. The digestion of the basal diet was also depressed, the apparent digestibility of dietary cellulose falling from 61.7 to 55.0%. 3. Three experiments with two sheep given liquid paraffin (mainly the C18 hydrocarbon) by infusion into the rumen showed that it had no effect on CH4 production and that it increased the excretion of fatty acids in the faeces and the non-lipid energy of the faeces. 4. Oleyl alcohol infused into the rumen of one sheep had no effect on CH4 production. It was excreted unchanged in large amounts in the faeces and increased the faecal excretion of fatty acids. 5. A preparation of sulphated C18 and Cla alcohols infused into the rumen of one sheep reduced CH4 production by 11.4 moles/mole sulphated alcohol. The preparation also caused a large increase in the excretion of non-lipid calories in the faeces and in the heat production of the animal. A larger amount of sulphated alcohols, given by infusion into the rumen of another sheep, reduced CH4 production to 41% of the initial values in 5 days, but caused refusal of food. 6. Two experiments were made with two sheep in which lauric acid was given by infusion into the rumen: Food refusals occurred within 48 h of commencing the infusion. 7. Sodium lauryl sulphate given to two sheep by infusion into the rumen reduced CHI production by 8.4 moles/mole. It greatly increased the faecal loss of non-lipid energy and also increased the heat production of the animals. When two further sheep were given sodium lauryl sylphate incorporated in the diet, cellulose digestion was depressed. Evidence of hydrolysis of the sodium lauryl sulphate was obtained. 8. Lauryl alcohol had no effect on the CH4 production of one sheep, but increased the faecal excretion of lipid. Inorganic sulphate had no effect on metabolism in an experiment with a further sheep. 9. The results, together with previous work with oleic, linoleic and linolenic acid (Czerkawski, Rlaxter & Wainman, 1966a), suggest that depression of CH4 production is a function of molecules with both polar and non-polar activities, that is with surface-active properties, and that such compounds when given to ruminants have a greater affect on the CH4-producing organisms than on organisms concerned in cellulose digestion.

1. The Chorleywood Bread Process is a new method of making bread in which the 2–4 h of bulk fermentation of the dough normal in breadmaking is replaced by a few minutes of intense mechanical agitation to a controlled degree in special high-speed mixers. It is now being used to make over 30% of British bread. 2. Bread was made in a commercial bakery from two white flours by the Chorleywood Bread Process and a conventional method. 3. Both the bread and flours were analysed for moisture, protein, ash, fat, carbohydrate (by difference), thiamine, nicotinic acid and ascorbic acid. 4. More bread was made by the two processes from two other flours in a pilot-scale bakery. These breads and flours were used to determine net protein utilization values. 5. It was concluded that bread made by the Chorleywood Process cannot be distinguished from conventional bread in its content of protein, fat, ash and nicotinic acid, and in protein quality as indicated by its net protein utilization value. This was true for two grades of flour. In these tests the contents of thiamine and moisture were slightly higher and of carbohydrate slightly lower in Chorleywood than in conventional bread. No ascorbic or dehydroascorbic acid could be detected in any of the bread.