1. Fatty liver was induced in 4-month-old male rats by oral dosing with ethanol. The marked increase in liver fat was not accompanied by a rise in lipid peroxides.

2. Homogenates were prepared from the livers of vitamin E-deficient rats and incubated with ethanol. In the concentration range of 10–50 μl/3 ml, ethanol increased the production of malondialdehyde. Methanol, which is not a hepatotoxin, showed a similar effect at 10–35 μl/3 ml homogenate. These findings indicate that the pro-oxidative effect of alcohols in vitro is unrelated to their hepatotoxic action in vivo.

3. Fatty liver was induced in 3.g-month-old, vitamin E-deficient male rats by oral dosingwith ethanol. The effect of pretreatment with vitamin E and N,N'-diphenyl-p-phenylenediamine (DPPD) was studied. D-α-Tocopheryl acetate, given as three doses of 350 mg/kg at 48, 24 and 2 h before the ethanol, failed to decrease the fat accumulation and seemed rather to increase the fat content of the liver. DPPD, given as three doses of 600 mg'kg at similar intervals before the ethanol dose, reduced the fat content of the liver almost to normal.

4. Weanling rats of both sexes were given a vitamin E-deficient diet containing 1% orotic acid for 15 days to induce fatty liver. Dietary supplements of D-a-tocopheryl acetate (500 ppm), selenium (I ppm) or DPPD (100 ppm) did not reduce the lipid accumulation. Lipid peroxides and malondialdehyde levels were lower in the livers of animals treated with orotic acid than in controls, regardless of the presence of vitamin E.

j. Liver necrosis was produced in 9-week-old female vitamin E-deficient rats by the intra-peritoneal injection of zoo mg thioacetamide. Promethazine hydrochloride (Phenergan), given intraperitoneally as two doses (25 mg/kg at the same time as the thioacetamide and 12.5 mg/kg 6 h later), markedly reduced the necrosis. D-α-Tocopheryl acetate, given as two oral doses of 1000mg/kg 48 h and 24 h before the thioacetamide, tended to exacerbate the necrosis.

6. The results are discussed in relation to the question of lipid peroxidation as a cause of hepatotoxicity.

1. In Expt 1, five groups of four dry non-pregant ewes were given 1 kg/day of a semi-purified diet containing either 0.05, 0.10 or 0.15% magnesium with 0 or 4.44% added potassium. Plasma Mg Concentrations were reduced by increasing the K intake (P < 0.001) and by reducing the Mg intake (P < 0.1). The effects were additive and, at the lowest Mg intake, supplementary K induced two cases of hypomagnesaemic tetany.

2. Expt 2 was similar to Expt 1 except that the ewes were suckling single lambs, they were given 2 kg food/day and the lowest dietary Mg concentration was 0.075%. K again lowered plasma Mg values and induced two cases of tetany but reductions in Mg intake had no effect.

3. After repletion on the basal diet, sixteen lactating ewes from Expt 2 were transferred to a diet containing 0.05% Mg with 0, 2.22 or 4.44% added K. Plasma Mg concentrations fell rapidly on each treatment; the effect was greatest in K-supplemented groups ( P < 0.05) and two cases of hypomagnesaemic tetany were induced at the highest K intake.

4. In each experiment the K supplements caused a rapid increase in plasma K concentrations to a relatively constant level some 5 mg/100 ml above the resting value of 18.0 mg/100 ml.

5. Some sheep refused K-supplemented diets at first and there was a tendency for refusals to be greatest at the lowest Mg intakes.

6. The results are discussed in relation to the aetiology of hypomagnesaemic tetany.

1. Several in vitro methods were compared with in vivo methods for estimating the nutritive value of leaf-protein concentrates (LPC), using a freeze-dried preparation from wheat (A) fresh, (B) after heating moist, (C) after heating moist and then extraction with chloroform, and (D) after extraction with an acidified solvent.

2. The treatments had little effect on the biological value (BV) of the samples for rats.

3. Heating moist decreased true digestibility (TD), net protein utilization (NPU) and protein efficiency ratio (PER), but the original values were almost restored by lipid extraction. Acidified solvent extraction decreased TD, NPU and PER of LPC perhaps by making it brittle and difficult to wet.

4. Papain solubility and TD were well correlated. Pepsin-pancreatin solubility and TD were less well correlated.

5. Microbiological estimations of available amino acids, involving predigestion with pepsin, correlated poorly with TD determinations.

6. Unsaturated fatty acids, particularly linolenic, formed complexes during heating of LPC. The effect of this on enzyme solubilization procedures and on digestion in vivo is discussed.

7. Some comparisons are made between the effect of heat and of extraction with solvents on LPC and on fish meal.

1. A combination of balance and isotope techniques has been used to study calcium metabolism at different stages of lactation in six sheep and the results have been compared with those obtained from four of the sheep 1 month after the end of lactation.

2. At first the animals were in negative Ca balance but, as milk yields decreased, so the animals moved progressively into positive balance.

3. Ca absorption from the gut was significantly increased throughout the whole of lactation but not sufficiently to meet the initial high demands for Ca.

4. Most of the extra Ca was supplied by bone resorption which was high in early lactation and decreased to a very low value at the end.

5. The rate of bone accretion remained constant throughout the period and was 1.5 times as high as in the non-lactating animals.

6. In the later stages, a combination of factors, but in particular a low rate of resorption of bone, enabled the animals to replenish some of the Ca lost from the skeleton in early lactation.

7. A month after the end of lactation replenishment of skeletal stores of Ca was still continuing as shown by the excess of bone accretion over bone resorption.

1. Rats were made severely iron-deficient by feeding with Fe-deficient diets, which contained adequate amounts of zinc.

2. Ten days after an oral dose of 250 μg65Zn the Fe-deficient rats had retained 17% whereas control rats had retained only 8% of the dose.

3. When unlabelled Zn was given intravenously to the Fe-deficient and control rats there was a reduction in retention of the orally administered 65Zn. This effect was not produced when Fe was given before the oral dose of 65Zn.

4. Total body Zn, whole blood Zn and plasma Zn concentrations of the rats were measured by atomic absorption spectrophotometry. Both the Fe-deficient rats and the control rats had the same total body Zn calculated as a proportion of body-weight. The plasma Zn concentrations were normal in all the animals. Blood cell Zn concentrations in the Fe-deficient animals were raised.

5. The blood cell Zn concentration was directly related to the reticulocyte count in all the rats.

6. It was concluded that Fe and Zn are absorbed by different metabolic pathways, and that there is an increased turnover of Zn in the Fe-deficient rats, possibly related to the short lifespan and increased Zn concentration of Fe-deficient rat erythrocytes. In the rat abnormalities of Zn concentration can only be considered significant if Fe status is also known.

1. The following techniques, which have been applied successfully to goats, were used to study mammary metabolism in lactating sows:(I) measurements of mammary arteriovenous (A-V) differences in milk precursors in the conscious undisturbed animal (five sows); (2) continuous intravenous infusion of [U-14C]glucose with concomitant arterial and mammary venous blood sampling for measurement of mammary blood flow and specific radioactivity of glucose and CO, (one sow); (3) perfusion of the isolated gland in vitro (eight glands from four sows), with the inclusion of [U-14C]glucose (two glands) and [U-14C]acetate(two glands) in the substrate mixture.

2. Sow mammary tissue was similar to that goats in its milk yield, blood flow, and glucose uptake per unit weight of tissue. As in goats, mammary uptake of glucose was many times that of the rest of the body and the total mammary tissue was utilizing about half of the total glucose entering the circulation. Glucose was a major source of milk lactose and glycerol and of mammary CO2.

3. Of the plasma lipid components, only the triglyceride fraction was consistently and significantly removed by the gland. In contrast to the results obtained for the goat, both [U-14C[acetate and [U-14C]glucose carbon were used for milk fatty acid synthesis, and although the pattern of labelling of fatty acid from each precursor was similar, the formation of fatty acids from glucose was at least five times greater than that from acetate. Quantitative evaluation of the contribution of these precursors was not possible, but the RQ (1.09–1.63) suggest that in some instances it may have been considerable.

4. The substantial A-V differences of most plasma essential amino acids suggest that these are the sole precursors of the corresponding residues in the mammary synthesized protein. The low A-V differences for several non-essential amino acids suggest that these are synthe- sized in the gland; this suggestion is supported by the incorporation of glucose carbon into non-essential amino acid residues of casein observed in one experiment. However, in contrast to results with the goat, mammary absorption of serine was consistently large.

1. The plasma levels of individual amino acids were studied in dairy cows under different conditions of production and energy nutrition.

2. A preliminary experiment was conducted which established that there was no regular change in amino acid levels with time of sampling in animals offered food twice daily at milking.

3. For animals in the 8th month of pregnancy plasma concentrations of lysine, valine, serine and isoleucine were higher, and of threonine lower, in Jersey than in Friesian cows. Lactation was accompanied in most cows by a fall in the plasma concentrations of lysine, arginine, threonine, histidine, glutamic acid, leucine and alanine and a rise in the level of glycine.

4. In lactating cows an improvement in the plane of energy nutrition was associated on average with an increase in the plasma concentrations of ‘non-essential’ amino acids and a decrease in the concentrations of ‘essential’ amino acids.

5. Intraruminal infusion of propionic acid in the lactating cow increased the concentrations of certain ‘non-essential’ amino acids, glutamic acid in particular, and decreased those of most other ‘essential’ and ‘non-essential’ amino acids.

6. These observations are discussed in terms of the possibility that an increased output of amino acids in milk proteins results in a depression in the concentrations of the ‘essential’ and certain of the ‘non-essential’ animo acids in the plasma. The hypothesis is put forward that the plasma supply of the other ‘non-essential’ amino acids, glutamic acid and proline in particular, may limit synthesis of milk proteins.

1. Compensatory, or ‘catch-up’, growth in eight malnourished children has been studied in relation to food intake, efficiency of food utilization and changes in body composition.

2. During recovery, growth rates were fifteen times as fast as those of normal children of similar age, and five times as fast as those of normal children of a similar height or weight.

3. Rapid growth was associated with a high food intake.

4. When the expected weight for height was reached food intakes fell abruptly by 30% and growth rates dropped to a level comparable with those of normal children of that height and weight.

5. Food conversion figures suggest an over-all increase in the efficiency of food utilization during rapid growth.

6. The percentage body fat increased, once the expected weight for height was reached.

7. Differences in the rates of weight gain from those predicted by the Miller-Payne equation were difficult to interpret: problems associated with the equation are discussed.

1. Piglets were left to suckle their dam for about 2 days after birth to obtain colostrum and were then divided into four groups. One group was left with the sow, the second was given a standard liquid diet based on cow's milk, the third the standard diet with lactic acid added to give a pH of 4.8, and the fourth the standard diet with the casein content increased by 50%. Stomach samples were removed at intervals by stomach tube for pH measurements and bacteriological investigations. The tube was used immediately to give barium sulphate for radiographic examinations and was then withdrawn. Comparisons were made between treatments and between scouring and non-scouring piglets.

2. A diarrhoeic (scour) syndrome frequently developed; this was always preceded by diminishing gastric activity leading to gastric stasis. When spontaneous recovery occurred, there was a return of gastric function before recovery from scours and before the resumption of normal weight gain.

3. The incidence, duration and severity of the scour syndrome was less in piglets left on the sow; these differences could not be ascribed to the effect of colostrum. Piglets receiving the lactic acid milk diet had an average gastric pH of 1 unit less than the other piglets. Although the severity of scour and loss of clinical condition was less in the piglets given lactic acid milk the duration of reduced stomach motility was the same as in the other artificially fed piglets.

4. No obvious correlation was shown between the scour syndrome and the bacterial flora of the stomach or the intestines. The gastro-intestinal tracts of the piglets given lactic acid milk contained fewer bacteria than those of the piglets on the other diets.

5. Gross between-treatment differences at post-mortem were evident only in the stomach.

6. The spontaneous scour syndrome observed under the conditions of these experiments appeared not to be of bacterial origin but to be associated with a physiological malfunction of the stomach.

1. An isotope dilution method, known to be satisfactory for measurement of volatile fatty acid (VFA) production in the rumen under steady-state conditions, was tested for its applicability where the VFA pool in the rumen could vary irregularly. The method indicated mean production rates closely similar to those obtained when the pool size was virtually constant. Tests carried out in a model rumen confirmed this finding and the method was accepted as suitable for measurement of VFA production in grazing sheep.

2. The method, modified to allow continuous sampling of rumen acids by dialysis, was applied to sheep grazing a mixed pasture. Mean rates of VFA production determined in seven sheep during fourteen 3-day periods throughout winter, spring and summer months ranged from 3.4 to 5.3 moles daily, production increasing during the period of growth of the pasture, and declining again with its drying-off.

3. The pasture was at all times abundant; the findings are therefore considered to represent the pasture's full potential yield of VFA to the sheep and so to indicate its changing value in this respect as the seasons progressed.

4. Results from sheep given roughages and from the grazing sheep indicated that, despite irregular intake, good predictions of mean VFA production rates could be made from mean VFA concentrations in the rumen fluid.

1. It was shown that when polyethylene glycol (PEG) was added to suspensions of food particles in aqueous buffer solutions, its distribution in the total water of the food mass was not uniform. The marker was excluded from a large proportion of the water contained in the swollen food particles. This effect was independent of temperature, pH, and, within limits, the time of contact.

2. It was shown that the theoretical concentration (C0), assuming a uniform distribution of marker, could be calculated from the observed concentration (C), weight of food in suspension (W) and the total volume of water (V), using the equation C = C0(I + b[W/V]) where b is constant for any given food. The addition of PEG solution to dry food particles gave a smaller effect.

3. The distribution of PEG was usually, but not invariably, more uniform in a suspension of roughages than in a suspension of concentrates.

4. Possible implications of these findings with respect to marker experiments with PEG are discussed.

1. Changes in blood sugar levels after giving carbohydrates have been used to assess carbohydrate utilization in pre-ruminant calves aged between 10 and 50 days.

2. Glucose, galactose and lactose were readily utilized by all calves; the utilization of glucose and galactose increased with age, whereas that of lactose remained constant.

3. Maltose and fructose utilization was low in young calves and increased slightly with age.

4. Sucrose and starch were not utilized.

5. Studies with three older pre-ruminant calves (aged 53, 88 and 106 days) in which the carbohydrates were infused into the proximal duodenum showed that glucose, galactose, lactose and xylose all caused marked increases in the level of blood reducing sugar, whereas fructose and sucrose caused no increase, and maltose was intermediate. Xylose and galactose caused very little change in the blood glucose concentration.

6. It appeared that preferential uptake occurred of glucose from a glucose-galactose mixture.

7. A non-linear relationship was found between the concentration of glucose or galactose infused and the increase in the level of blood reducing sugar.

1. A semi-synthetic vitamin B12-deficient diet, based on soya flour, is described. When supplemented with cydnocobalamin the diet appeared to be adequate for growth and reproduction in the rat.

2. Compared with their litter-mates on the supplemented diet, rats fed on the deficient diet from weaning showed reduced levels of vitamin B12 activity in the plasma and tissues, but their growth rates were unaffected unless they were bred from mothers that had been given the deficient diet since mating.

3. When they were reared on the deficient diet, rats bred from mothers on the deficient diet since mating excreted much more methylmalonic acid in the urine than their litter-mates on the supplemented diet. There was wide variation in the level of excretion, both between different animals and from day to day in the same animal.

4. Starvation for more than 16 h caused a marked depression in the amount of methylmalonic acid excreted by rats on the deficient diet.

5. Intraperitoneal injection of sodium propionate into deficient animals after starvation for 24 h caused increased excretion of methylmalonic acid during the following 16 h of continued starvation. Isoleucine had a similar but smaller effect.

6. Tested in the starved animal, sodium propionate and valine given either by intra- peritoneal injection or by mouth, and isoleucine given intraperitoneally, caused increases in the excretion of methylmalonic acid. In contrast, methionine had no effect and threonine only a slight effect.

1. Studies were made of the fermentation of D-glucose, D-fructose, D-galactose, D-xylose, L-arabinose and sucrose by rumen contents from two cows fed 1 kg hay and 4 or 5 kg flaked maize once daily. The proportions of volatile fatty acids (VFA) in the rumen before addition of carbohydrates varied widely but on average acetic acid constituted about 52%, propionic acid about 29% and n-butyric acid about 13% of the total.

2. In in vitro experiments, 896 mg of the monosaccharides and 851 mg sucrose were added to 150 g mixed rumen contents incubated for 2 h; the carbohydrates were added at 10 min intervals throughout the incubation on three occasions with each cow. Mean proportions of the carbohydrates fermented ranged from about 60% of the pentoses to about 85% of sucrose and glucose. Of the VFA produced from galactose and the pentoses, acetic acid constituted about 40%, propionic acid 45–55% and n-butyric acid 1–7%; very little n-valeric acid was produced. With the other carbohydrates results from the two cows differed, owing mainly to the production of appreciable amounts of n-valeric acid with one cow only. Acetic acid constituted about 40% of the VFA produced from fructose and sucrose, propionic acid 20–40%, n-butyric acid 14–22% and n-valeric acid up to 12%. The proportions of VFA produced from glucose were intermediate between the other two groups.

3. Net recovery of carbon from fermented carbohydrate in VFA was about 35–45%. A further 1–6%, of fermented glucose, fructose and sucrose was recovered in lactic acid.

4. In in vivo experiments, the monosaccharides only were infused into the rumen for 8 h at the rate of 200 g/h. Changes in the concentrations of substrates and products varied widely, owing to the variable basal fermentation, but changes in the proportions of VFA in the rumen were similar to those found in vitro.

5. The results of the in vitro experiments were compared with those obtained in earlier experiments in which the same cows were given a diet containing 70% hay. Significant regressions (P < 0.05) were found between the molar proportions of acetic, propionic and n-valeric acids produced from the substrates and the proportions of these acids present in the rumen contents at the start of the incubations, but the relationships differed markedly among the different carbohydrates. Most of the significant regressions were positive but negative regressions for propionic acid production from fructose and sucrose with one cow suggested the existence of more complex interrelationships among two or more VFA.

1. ě-N-Acetyl-L-lysine showed a growth-promoting value for the young rat receiving a lysine-deficient diet approximately half that of the equivalent quantity of L-lysine; ě-N-propionyl-L-lysine showed negligible activity.

2. Considerable quantities of lysine were recovered from acid-hydrolysis of the urine of rats receiving these two compounds. Qualitative chromatography suggested that the compounds themselves were appearing in the urine.

3. Similar results were obtained from giving proteins that had the ě-NH2, groups of their lysine units either acetylated or propionylated.

4. Giving a pure protein in which the nutritional availability of the lysine had been reduced heat treatment resulted in greatly increased faecal lysine but little urinary lysine.

1. The biological evaluation of solvent and prepress-solvent processed rapeseed meals RM(S) and RM(PS) was carried out with the weanling (phase 1) and the mature (phase 2) rat. The nutritional indices measured were compared with those for diets containing soyabean meal SM and casein CS.

2. The true nitrogen digestibility (td(N)) for RM(S), RM(PS), SM and CS in the weanling rat was (%) 78.9 f±1.2, 77.9±2.7, 90.4±0.9 and 96.0±0.6 (P < 0.01) respectively. Net protein utilization was (%) 68.9±10.1, 65.6±3.5, 80.6±4.8 and 81.7±3.1 (P < 0.05) respectively. Biological value was (%) 83.0±7.9, 84.1±5.6, 8.90±5.1 and 85.0±3.4 (P < 0.05) respectively. The same indices when measured in the mature rat showed an increase over those obtained in the weanling rat.

3. The growth-promoting effects of the test diets were evaluated over a period of 8 weeks with ad lib. feeding between phases 1 and 2. Protein efficiency ratio averaged 2.0±0.14, 1.9±0.35, 2.4±0.39 and 2.3±0.25 for the RM(S), RM(PS), SM and CS treatments respectively.

4. The daily endogenous urinary N excretion was 1.58±0.14 mg N/basal kcal or 254 mg N/kg body-weight for the weanling rat and 0.16 mg N/basal kcal or 18 mg N/kg body-weight for the mature rat. Metabolic faecal N excretion was 98.0±9.3 mg N/kg body-weight, or 27.9% of the total N output for the weanling rat, and 37.9±7.2 mg N/kg body-weight, or 67.3% of the total N output for the mature rat during the ‘protein-free’ feeding periods.

5. The fresh weight of the thyroid gland per kg metabolic body size was 70, 90, 40 and 40 mg respectively for the RM(S), RM(PS), SM and CS dietary treatments.

6. The moisture content of the carcasses was 66.9±3.1, 63.6±2.3 and 64.2±2.2 and the protein content on a dry-matter basis was 55.9±9.6, 50.2±6.4 and 53.1±4.9 for the RM (S and PS), SM and CS diets respectively. The results suggest an increased lean body mass in the rats receiving the rapeseed meal treatments.

7. Under the conditions of this experiment solvent-extracted rapeseed meal was superior to prepress-solvent meal on the basis of rat growth response and of results for nutritional indices. Both rapeseed meals were inferior to soya-bean meal and casein.

1. Four wether sheep, each fitted with re-entrant duodenal cannulas and a rumen cannula, were used to determine the relative quantitative importance of digestion in the stomach compared with that in the intestines when diets of low (HM1) and high starch (CM1) content were fed at 0.9 times maintenance and when the high-starch diet was fed at 1.7 (CM2) and 2.3 (CM3) times maintenance. Paper, impregnated with chromic oxide, and polyethylene glycol (PEG) were administered.

2. An apparatus is described which allowed one operator to collect, record, sample and return the duodenal digesta from two sheep simultaneously.

3. Total digestion was determined by faeces collections over 7–10 day periods, and digestion in the stomach by measuring the total flow of digesta from the abomasum to the duodenum over two 24 h periods with two or three sheep on each ration. Flow values were adjusted to give 100% recovery of chromic oxide.

4. The recoveries of chromic oxide and PEG were similar and it was concluded that either marker was satisfactory for adjusting 24 h flow values. Disadvantages of using PEG are discussed.

5. There was relatively little difference between rations HM1 and CM1 in the proportion of digestible organic matter and energy digested in the stomach. Only 57.1% of the total dry-matter digestion occurred in the stomach for ration HM1 compared with 65.0% for ration CM1 reflecting a smaller net gain in ash for ration CM1. Doubling the level of intake (ration CM2) resulted in a decrease in the proportion of digestible dry matter, organic matter and energy digested in the stomach. When the level was increased still further with ration CM3, the proportion continued to decrease with one sheep but increased with the other.

6. All but 5–11% of the digestible starch (measured as α-linked glucose polymer) was fermented in the stomach, the lowest proportion being with ration HM1.

7. The amount of nitrogen reaching the duodenum was approximately equal to the amount ingested with rations HM1 and CM1 but considerably greater with the other two rations. All rations contained approximately 2% nitrogen.

8. Calculation of the estimated loss of energy as methane and heat of fermentation suggested that 50–54% of the digestible energy was absorbed as volatile fatty acids.

1. Individual body fat and body measurements such as lengths, girths and selected skinfold thicknesses were determined in our laboratory strain (BHE), a highly inbred strain (IN) of BHE rats and in a strain of Wistar rats. Measurements were made on unconscious rats in less than 5 min per rat just before autopsy; body fat content was determined in individual rats of both sexes at 50, 100 and 300 days of age.

2. Among the strains, mean total body fat was highest in BHE rats at each age; IN rats of similar average body size were leanest. Statistically significant differences in body fat among the strains were due primarily to differences among the male rats at 300 days. Total protein and skeletal mass increased with increases in age and body size, as did body fat in rats after maturity. IN rats had the largest fat-free weights. Although significant age differences in body fat and body measurements occurred, they were in part dependent upon changes in body- weight, sex and strain of the animals. Female rats had more fat per unit body-weight than males at each age studied. Females, though fatter than males, had smaller skinfold thicknesses, indi- cating that female fat increases are primarily in visceral fat.

3. Large variation in fat among individuals within strains of the same body-weight and age suggests a genetic influence in fat potential in rats not associated with age or body-weight.

4. Results from multiple regression analyses showed differences among adjusted means and partial regression coefficients due to strain and sex of the animals. Although final body-weight was the predictor common to all equations, body length, abdominal girth and subscapular skinfold were common to all but one set of equations. Chest girth, tibia length, triceps and abdominal skinfolds decreased in frequency of appearance in that order. Some of the measurements were more effective predictors at one age than at another. It was clearly necessary to take into account body dimensions other than weight to obtain an optimal prediction of body fat.

5. Differences in characteristics of the rats support the concept of genetic influences in fat deposition in individuals and indicate the complex nature of these influences.

1. Sheep were given intraruminal infusions of maize oil or linoleic acid and samples of contents were taken from the rumen and abomasum at different times after the infusions. Hydrolysis of the maize oil occurred in the rumen with the production of mono- and di-glycerides as intermediates. Linoleic acid derived from the maize oil was hydrogenated to stearic acid. When linoleic acid was infused into the rumen, little or no stearic acid was produced and octadecenoic acid accumulated.

2. When linoleic acid or maize oil was incubated with rumen contents in an artificial rumen and samples of the reaction mixtures were taken from the apparatus after various time intervals, the results were similar to those obtained in vivo, except that the hydrolysis of maize oil did not give rise to mono- and di-glycerides.

3. These results are discussed in relation to previous findings on the effects of intraruminal infusions of maize oil or linoleic acid on the fatty acid composition of the blood triglycerides of sheep.

1. Seven groups of male rabbits (thirteen to fifteen per group) were given ad lib. a diet consisting of 80 parts of a low-fat basal ration to which were added 20 parts of fat in the form of butterfat, maize oil or various mixtures of the two.

2. After 40 weeks, samples of blood were taken and the animals were killed. The concentrations of total cholesterol and phospholipid in the plasma and the fatty acid compositions of the plasma cholesteryl esters and phospholipids were determined. The degree of atheromatous degeneration was determined in the aortas.

3. Little aortic atherosis was observed in the rabbits given the diets containing 0, 10 and 12% butterfat, but as the butterfat content of the diet was increased above 12%, pronounced increases occurred in the extent of atheromatous degeneration of the aorta. The concentration of cholesterol in the plasma increased progressively as the butterfat content of the diet was increased and the maize oil content was decreased. There was an inverse curvilinear relationship between the degree of aortic atherosis and the phospholipid: cholesterol ratio in the plasma.

4. The concentration of linoleic acid in the plasma cholesteryl esters was inversely related to the concentration of cholesterol in the plasma, and the concentration of linoleic acid in the plasma phospholipids was inversely related to the concentration of phospholipids in the plasma. There was a positive linear relationship between the stearic: palmitic acid ratio and the linoleic: oleic acid ratio in the plasma phospholipids.