1. Diethylstilboestrol administered orally to a Shorthorn cow had no marked effect on milk yield or composition.

2. A series of injections of the dipropionate in oily solution led to a slight rise in non-fatty solids in the same cow as in 1. Single larger injections were followed by a rise in milk solids accompanied by a rapid fall in milk yield in two other Shorthorns.

3. Inunction with an ointment containing the dipropionate led to a marked increase in milk solids in a Shorthorn cow, with no change in milk yield. The effect subsided rapidly when treatment was stopped. No significant effects were produced by similar treatment of four pregnant British Friesians; on increasing the dose two of these aborted. A Guernsey cow showed a slight increase in nonfatty solids and a slight but temporary fall in milk yield.

4. Subcutaneous implantation of crystalline diethylstilboestrol led to a striking and prolonged increase in milk solids, with no fall in milk yield, in a Shorthorn cow.

5. Subcutaneous injection of an aqueous suspension of diethylstilboestrol (1 g.) was equally successful when applied to the same cow as 4, but in the next lactation. In three Ayrshires the increase in solids was accompanied by an appreciable decline in milk yield. A Shorthorn receiving 375 mg. showed a temporary rise in solids, while one receiving 225 mg. showed no effect.

6. In all cases where milk yields declined the milk solids percentage rose, but the converse did not hold. Hence the threshold dose for inhibition is apparently higher than for enrichment.

7. The threshold doses may depend on the breed; the most successful results were obtained with Shorthorns.

8. Treated cows may be difficult to get in calf subsequently, especially those treated twice.

9. Administration of large doses of diethylstilboestrol to cows in advanced pregnancy results in abortion.

10. The enrichment of the milk in favourable cases represented a true increase in the yield of solids secreted, and not merely a concentration due to reduced secretion of water.

Lancefield Group B streptococci have been recovered from the hands of milkers even in herds where infection was very light. Since these organisms had the biochemical reactions of Str. agalactiae, and since none were recovered from the hands of non-milkers, it is considered that they were identical with this organism and that the milkers' hands are a potential source of danger to cows. The methods of disinfection at present in use have been criticized and suggestions for improvements made.

In a preliminary investigation into the experimental error of the plate count examination of butter, 154 boxes of choicest quality butter were examined by plating in triplicate, in a dilution of 1/500, each of three 1 g. samples per box.

X2 tests in both this and a later series indicated that the means of the triplicate counts in respect of plates averaging less than 300 colonies gave, in the main, reasonably satisfactory estimates of the bacterial content of the samples. In two of the tests, however, excessive within-sample variability was shown by abnormally high values obtained from the summation of x2. This is accepted as an indication that the plate count was not always a reliable index of the sample population.

The between-sample variability in this series has been shown by transforming the counts to logarithms and calculating the coefficient of variation in respect of each box. In the distribution of the coefficients approximately 50% were found to lie on either side of a 4·0% level, while 10% gave values higher than 14·0%.

In a further inquiry twelve boxes of butter were selected for quality and uniformity and data were secured from the examination of seven 1 oz. samples selected at random from each box.

Treatment of the results by the method of analysis of variance, using a square root transformation, indicated that the estimates of within-sample variance obtained could be regarded as estimates of a common variance. Highly significant differences were found, however, among the between-sample mean squares, and the variability was found to be excessive in six of the twelve boxes examined.

No significant general correlation was found in this series between bacterial counts and either salt or moisture determinations.

The application of these results to research problems and to routine tests involving the estimation of bacterial numbers in butter is discussed.

Two cases of “slowness” in cheesemaking are reported in which the trouble was eliminated by changing the source of the starter.

Attempts to isolate either bacteriophage or “non-acid” organisms failed.

Abnormal milk had no effect on the rates of acid production when compared with control normal milk.

A fall in the acidity of the whey draining from the cooler was observed.

The inability of certain strains of streptococci to grow at scalding temperatures appears to be one cause of “slowness” in cheesemaking.

1. The pitching consistency of some 470 cheese has been determined at one factory and the data compared with the subjective judgements of a skilled cheesemaker. The smallest difference in consistency which the expert can distinguish with a reasonable degree of accuracy (threshold) is compared with those for purely elastic and viscous bodies, and it is concluded that the consistency at pitching is judged mainly from the elastic properties of the curd. The good agreement between these thresholds substantiates the hypothesis that our test for pitching consistency is closely related to the requirements of the practical cheesemaker.

2. The connexion believed to exist between firmness of curd at pitching and acidity was not substantiated, in the case of Cheddar, by a statistical examination of the available data.

3. The most usual values (medians) for pitching consistency are compared for four different factories, and it is shown that differences in technique may be associated with the same pitching consistency and produce very similar cheese, but that in other cases good cheese may be produced from very different pitching consistencies. The important thing is that the pitching consistency should be known and controlled so as to be as constant as possible under given conditions.

4. A technique is described for measuring the force required to thrust a skewer into cheese. This force (S) is highly correlated with “body” judged subjectively by an experimenter who was aware of the fact that such a correlation was to be tried. Judgements of “body” made by expert cheese graders were not so correlated, but the interpretation of their judgements was inadequate, so that no definite conclusion can be drawn.

1. Methods for measuring the vapour pressure of cheese and milk are discussed, and vapour pressure/moisture curves are given for a number of different varieties of cheese. The progressive artificial damping and drying of cheese produces no appreciable hysteresis in these curves.

2. The vapour pressure curve is much influenced by the amount of salt in the cheese, but differences between varieties cannot be accounted for entirely in terms of differences in NaCl content.

3. A preliminary experiment on the relationship between vapour pressure of Stilton cheese and amount of blueing indicated that such a relationship does in fact exist but that a much larger experiment is required before the connexion is fully understood.

4. Preliminary experiments on the measurement of the vapour pressure of milk, although interrupted at rather an early stage, showed that, even so, additions of 2–3% of water in milk can be satisfactorily detected.

Bacteriophages for lactic streptococci were found to occur in the atmosphere of commercial cheese factories. Finely divided particles of whey emitted from the whey separator appeared to be the main vehicle for the air-borne phage although whey-contaminated dust probably also played a part. The concentration of air-borne phage was sometimes so great that, with the use of a normal bacteriological aseptic technique, it was impossible to prevent infection of the starter cultures for more than a few propagations. Protection of the starter from air-borne phage eliminated phage failures.

The question of the origin of bacteriophage is discussed in the light of the recognition of the prevalence of air-borne phage. The occurrence of air-borne infection could account for most of the instances of starter failures which were previously thought to be due to spontaneous phage development within cultures.

1. Experiments have been carried out in order to determine the best method of neutralizing cheese whey prior to drying by the roller process. The use of sodium or potassium compounds leads to difficulties in drying and the production of an unpalatable product of poor quality. Neutralization with calcium hydroxide gives a satisfactory product. Over-neutralization must be avoided.

2. Complete neutralization of hydrochloric acid casein whey results in the formation of a flocculent precipitate and deterioration in the drying properties; reduction of the acidity from 0·48 to 0·18% by the addition of calcium hydroxide allows successful drying and yields a reasonably satisfactory product. The latter is, however, definitely unpalatable.

3. Acetic acid casein whey can be dried without any previous neutralization to yield an excellent and palatable product.