The viscosity of cream increased with increasing fat content, and higher values were obtained if the cream was separated at 38–43 °C rather than above 55 °C, and if the cream was cooled to below 15 °C before storage at 20 °C. The ‘type’ of viscosity varied with cooling and storage conditions; for example, cream cooled below 20 °C and stored at 20 °C gave increased viscosity readings with increased rates of shear due to churning of the cream, while the behaviour of cream cooled only to 20 °C was Newtonian.

Cream stability as measured by free fat content decreased with increasing fat content above about 42%, with low temperature separation (38–45 °C), with cooling to below 15 °C before storage at 20 °C, and with increased pressure at temperatures below 15 °C.

Dilatometric study of the amount of fat crystallization indicated that larger amounts of crystallization resulted in higher final viscosity and free fat content.

The fatty acid composition of colostral and milk fat samples representative of the total secretion of the nursing mammae of each of 3 sows was determined by gas-liquid chromatography. In both colostral and milk fats, acids of chain length C16 and C18 accounted for more than 90% of the total fatty acids present; colostral fat contained a higher proportion of oleic acid and linoleic acid and less palmitic acid and palmitoleic acid than normal milk fat. Structural studies on milk triglycerides showed that, as in pig depot fat, palmitic acid is preferentially esterified to the secondary alcoholic group (2-position) of the glycerol molecules with the C18 acids (stearic, oleic and linoleic acids) being present for the most part in the 1- and 3- positions.

Coagulase-negative staphyloccoci were isolated regularly over a period of 39 weeks from quarter milk samples of 18 cows belonging to one herd. They did not produce a leucocytosis in the milk or high anti-haemolysin titres in the blood of these cows, but such responses occurred in 2 cows infected with pathogenic staphylococci. The coagulase-negative variety was found to colonize the teat duct and surface of the teat in preference to the milk and possessed greater resistance than pathogenic staphylococci to certain long-chain fatty acids. Infection with coagulase-negative staphylococci was thought to antagonize the colonization of the udder by a pathogenic variety present in the herd; 23% of the coagulase-negative strains were found to elaborate an antibiotic substance inhibitory to the growth of a coagulase-positive staphylococcus. Coagulase-negative strains were characterized by the production of ɛ-toxin and could be divided into 3 main groups according to their effect on gelatin, mannitol and phenolphthalein diphosphate as substrates.

An antibiotic produced by coagulase-negative staphylococci isolated from the bovine udder was examined by deferred antagonism tests and its inhibitory properties compared with those of other staphylococci. While inhibiting the growth of representative phage types of bovine pathogenic staphylococci, its activity against corynebacteria was more restricted than that of Staphylococcus aureus NCTC 6507 and 8004. Only minimal amounts of inhibitory substance were produced in liquid media, larger amounts were produced on solid media and the incorporation of a blood plasma factor further increased production. The inhibitory substance resisted treatment with pepsin and trypsin and withstood boiling for 30 min. Its characters in relation to inhibitory substances produced by other staphylococci are discussed.

Casein derived from the micelles of milk by removing the calcium has been subjected to partition and counter current distribution between phases containing polyethylene glycol and dextran. The results show that at least 2 kinds of casein complex exist which differ in structure, in size or in both. There are also differences in composition with respect to minor components, though both types contain predominantly α- and β-casein.

Injections of l-thyroxine into normal dairy cows at the beginning of lactation resulted in animals fed on a high protein diet becoming ketotic. Some of the symptoms observed in the induced ketotic cows showed many similarities when compared with those associated with the spontaneous condition.

In most cases the levels of the constituents estimated in the blood of the induced ketotic cows were similar to those measured in blood from spontaneous cases. A histological examination of the liver from an induced ketotic cow showed a considerable increase in the fat content, particularly in the centrilobular regions. The fat content of this tissue amounted to 26% with a concomitant depression of liver glycogen to only 10% of the normal level.

Diet was found to play an important role in the susceptibility of cattle to the induced ketosis, since animals fed on rations containing a lower level of protein were more resistant. Attempts to induce ketosis in cows 6—8 months after calving were completely unsuccessful.

The part played by the thyroxine and the diet in the induction of ketosis is discussed.

Strains of Lactobacillus bulgaricus and Streptococcus thermophilus isolated from yoghurt culture were used to study the cause of the synergistic effect on acid production by mixtures of the 2 cultures. The beneficial effect was essentially limited to the gradual accumulation of factors in the L. bulgaricus cultures that promoted more rapid acid production by Str. thermophilus. The active factors were identified as glycine and histidine.

The entry into milk from blood of N-acetyl-4-aminoantipyrine (NAAP) and urea, compounds known to be distributed evenly throughout the whole of body water, and thiocyanate and thiosulphate, the distribution of which is confined largely to extracellular fluid, has been investigated. The concentrations of NAAP and urea in blood and in milk were similar, but the concentrations of thiocyanate and thiosulphate in milk were much lower than the concentrations in blood plasma. A progressive increase in the ratio of the thiocyanate concentration in milk to that in blood occurred with advancing lactation and marked variations in the thiocyanate ratio of the milk of the separate quarters were observed in some cows, and these variations in the ratio were closely related to variations in the chloride content of the milk; similar inter-quarter variations in the ratio for NAAP were not observed. With NAAP, there was a continuous equilibrium between blood plasma and milk within the udder, whereas with thiocyanate the content in milk after its secretion into the ducts and cisterns of the udder appeared to be largely independent of later changes in the concentration of thiocyanate in blood plasma. These results are discussed in relation to the secretion of chloride in milk.

Using several milk supplies, a comparison has been made between the amount of deposit formed under standard conditions in a small plate type ultra-hightemperature heater, and the results from the hot-wire laboratory apparatus described previously. It is shown that the laboratory apparatus reproduces the variations in the sensitivity to deposit formation found using the plate heater. The relationship is linear if the criterion derived from the hot-wire results is taken as the square of that proposed previously. A decrease in the sensitivity to deposit formation during the ageing of fresh milk, and a seasonal variation, are indicated.

Fifty-nine strains of pediococci were isolated as representing the predominant non-starter flora in a series of Cheddar cheeses made over a period of 5 months. All strains had the same physiological characteristics and were identified as Pediococcus cerevisiae. A common antigen was found in 54 of the strains, whereas in the other 5 the antigenic component appeared to be related but not the same. Both antigens were located in the cell wall.

All the strains required folinic acid for growth and it was shown with one strain that the small amount of growth which occurred in sterile milk was greatly increased by the presence of the folinic acid producing starter Streptococcus cremoris 924.

Phytanic acid, 3,7,11,15-tetramethylhexadecanoic acid, which hitherto had been isolated and identified from several natural sources including butterfat, ox perinephric fat and cow plasma, has now been found present in small amounts (2·9%) in the total fatty acids extracted from the rumen bacteria of a fistulated dairy cow fed a diet of clover-grass hay. This C20 multibranched fatty acid was not detected in the dietary clover-grass hay, and it is considered to have been derived from phytol by enzymic activity of the rumen bacteria.