1. A simple method is described for the determination of carotene and vitamin A in milk. Figures for the carotene content of milk were higher and those for vitamin A were lower than similar figures reported by Western workers.

2. Figures for vitamin C in milk are similar to corresponding figures of English and American workers. Previous low values for vitamin C, reported by Indian workers, are due to destruction of the vitamin by light.

3. The vitamin C concentration of milk is not subject to great individual variation, probably because cows cannot excrete in milk any vitamin C taken in with the food and because vitamin C of milk is produced by synthesis within the mammary glands from some simple blood constituents.

4. To test the ability of bovines to synthesize vitamin C, young calves were kept for long periods on a strictly vitamin C-free diet. The concentration of vitamin in the blood and other tissues of these animals remained, however, at a normal level. Calves appear therefore to be able to synthesize sufficient vitamin C for their normal growth and activity.

5. Unsuccessful attempts were made to produce vitamin C in vitro by growing bacteria isolated from various parts of the alimentary canal on media prepared from ingesta taken from the regions from which they were isolated.

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.

1. Observations on five animals indicate that the teats of immature castrated male goats grow isometrically. Less extensive data on three animals allow of the tentative conclusion that the same is true of immature normal males. In the male goat therefore teat growth appears to be uninfluenced by the testes.

2. Administration of diethylstilboestrol or its dipropionate to normal or castrated immature male goats causes the teats to grow allometrically for a time.

3. No externally visible udder growth occurred even when oestrogen treatment was prolonged for periods of over a year and was supplemented by progesterone or ethinyltestosterone. Whole mounts of glands from treated animals indicated that some mammary growth had occurred. In two cases microscopic examination showed the presence of alveoli. No explanation can be offered of the failure to develop the udder in the male goat experimentally.

4. Endocrine activity of the ovary as evidenced by a change from isometric to allometric teat growth often manifests itself in the young female goat at an early age. In one case allometric teat growth was in progress at 41 days of age. During the allometric phase the data agree with the simple allometric law.

5. During the rutting season following its birth, teat growth ceases completely in the female goat; allometric growth is resumed when the rutting season ends. It therefore appears that the corpus luteum inhibits teat growth.

6. Administration of diethylstilboestrol or its dipropionate (by inunction of the udder region) causes, in the virgin female, an increase in the rate of teat growth accompanied by udder growth.

The total solids of samples of ass's milk ranged from 7·80 to 9·10, the solids-not-fat from 7·14 to 8·50, and the fat from 0·54 to 0·71%.

The nitrogen distribution in ass's milk is: casein 39·5, albumin 35·0, globulin 2·7 and non-protein nitrogen 22·8% of the total nitrogen. Ass's milk contains: casein 0·70, albumin 0·62 and globulin 0·07%. The total protein content is 1·39%. Ass's milk is therefore characterized by a low casein, a low globulin and a high albumin content.

The non-protein nitrogen consists of amino nitrogen 8·1, urea nitrogen 24·3 and uric acid 0·7 mg./100 ml. of milk. The urea content is twice that present in cow's milk.

The mean chloride and lactose contents of the milk samples are 0·037 and 6·1% respectively.

The average calcium and phosphorus content of ass's milk are 0·081 and 0·059% respectively. Half the calcium is ionic, and half is in colloidal form.

The phosphorus distribution is: total acid soluble 84·0, acid soluble organic 38·5, easily hydrolysable ester 27·4, inorganic 46·0, and colloidal inorganic 23·0 % of the total phosphorus. The ratio of CaO: P2O5 is 1:1. 46 % of the total phosphorus is in ester form; this is high when compared with only 12 % in cow's milk; most of the phosphoric ester forms soluble barium salts, which is a distinguishing feature of ass's milk.

The total sulphur content is 15·8 mg./100 ml.

The fat has a penetrating odour and is coloured orange-yellow. It has an iodine value of about 86, which is much higher than that for human milk fat. The Reichert (9·5) and Kirschner values (5·7) are low.

In general, the composition of ass's milk resembles that of human rather than of cow's milk.

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.

1. Defining sensitivity as the power of discriminating significantly between milks of different bacterial constitution the plate count is slightly less sensitive than the methylene-blue test observed every 5 min. and slightly more sensitive than the latter observed every half-hour.

2. The logarithm of the plate count is, in our opinion, the correct measure to use. Its coefficient of variation is slightly less than that of the methylene-blue test observed every 5 min.

3. The plate count as formerly used and the methylene-blue test as now used agree in grading in over 80% of cases.

4. Two samples whose reduction times differ by 30 min. are not significantly different. Such a difference is only significant if the result is based on the mean of duplicate tests with 5 min. observations or of triplicate tests with half-hourly observations.

5. Provided transit hazards are eliminated and standard technique is very carefully observed, there is no significant difference in results from different laboratories by either test.

6. Neither test necessarily reflects minor changes or faults in production routine. Under the conditions of our experiment the methylene-blue test was not, in cold weather, a satisfactory indicator of the numbers of organisms as distinct from ‘activity’.

1. The direct volumetric copper reduction method of estimation of lactose in unclarified milk gives results which are in good agreement with those on the same milk clarified and decalcified.

2. For the polarimetric' or iodometric methods of estimation of lactose the milk is best clarified with either zinc hydroxide or cadmium hydroxide. Clarification with acid mercuric nitrate or phosphotungstic acid for the polarimetric method and with dialysed iron or phosphotungstic acid for the iodometric method gives high results owing to failure to remove interfering substances.

3. Dialysed iron, phosphotungstic acid, cadmium hydroxide or zinc hydroxide are all suitable for deproteinizing the milk for the chloramine-T method of estimation of lactose.

4. The values for lactose content of milk as estimated by the above methods show good agreement and therefore may be accepted as the true milk sugar content.

The results of regular determinations of the freezing-point and solids-not-fat content of the milk of three Shorthorn cows over a period of more than six months are reported.

The known constancy of the freezing-point depression was confirmed, the Δ values deviating generally by less than 2% and, in the most extreme case, by no more than 3·5% from the mean of 0·546 ± 0·002° C. No evidence was found of any influence of the state of lactation on the freezing-point depression, but a slight but definite decrease persisting for some weeks occurred at the time of year at which ample supplies of spring pasture became available to the animals.

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.

Scott Blair & Coppen(I) have described a test for the consistency of firm cheese curd during the process of scalding and at the pitching point. This test gives the cheese maker an objective physical measure of a property which he is used to assessing subjectively by handling the curd, and should ensure a more constant condition in the curd from vat to vat and from day to day.

In the course of attempts on a field scale to eradicate or control Str. agalactiae infections, comparisons of the efficiency of several bacteriological methods have been made. It has been found that by using a method of enrichment, many cases of infection with small numbers of Str. agalactiae can be demonstrated in animals which give negative results by other methods. The frequency of examination has been shown to have an important influence upon the number of positive cases discovered.

Light infections have been, proved to persist for long periods. Light infections with Str. dysgalactiae and Str. uberis have also been found in many cases. Str. agalactiae has been shown to be present in no less than 21 % of animals in their first lactation and 4·5 % of heifers were found to harbour this organism whilst in isolation before joining the herd. The bearing of these findings on the theory of contagion in Str. agalactiae infections has been 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.

Trials with the Scott Blair apparatus for measuring hardness of butter by compression of a cylindrical sample showed a lack of reproducibility due to splitting or crumbling of the sample. Investigation of alternative methods led to the development of an apparatus in which the resistance of butter to cutting by a wire is measured. The method gives results which are in general agreement with those obtained with the Scott Blair apparatus, but are much more reproducible. The effect of wire diameter and thickness of block of butter have been determined, and conditions for temperature control of the sample before and during the determination have been investigated.

1.Details are given of the extraction method for the estimation of the volatile acids in cheese, as used in the study of some white and blue-veined varieties.

2. On the basis of the distribution of valatile acids, hydrogen-ion concentration and nitrogen breakdown, distinctions could be drawn not only between the white and blue-veined varieties as a whole, but also between the Roquefort and Stilton groups of the latter varieties.

3. A high total quantity and a characteristic distribution of the volatile acids appeared to be related to the heavy pricking of cheese of the Roquefort group.

1. Six cheese of Cheddar type were made under conditions as similar as possible, except that the consistency of the curd at pitching, and in two cases the rate of scald, were varied.

2. Chemical and rheological analyses, as well as measurements of moisture content and vapour pressure, were made on the cheese and also judgements of firmness under various conditions were given by cheese-makers, bakers and non-experts.

3. A table is given in which the orders of placing of the cheese are compared as between the objective tests and the subjective judgements. The cheese-makers and the non-expert testers gave, in general, characteristically different orders, the orders given by the bakers tending to fall between the two.

4. It appears that the consistency of the curd at the pitching point (W/h as determined by the Scott Blair-Coppen method) and probably the rate of scald, are prime factors in determining the firmness of the cheese.

5. The whole experiment is preliminary in character and it is intended to repeat it in an extended form in the near future.

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.

It has been shown that the rate of shear of butter when cut by a wire increases as a power of the load applied to the wire. The values of this power are high (index n = 8 to 15, average 11 at 12.5° C.) and show a high structural viscosity in the butter. There is no indication that butter exhibits a true yield value, but the (rate of shear)/(load) curve is such that a practical yield value is found. The practical yield value (denned as the minimum load required to produce a measurable rate of flow) provides a convenient measure of the hardness of butter. The viscosity of butter decreases rapidly as rate of shear is increased, but the rate of decrease varies from one sample to another. Measurements of spreading capacity should be made at rates of shear comparable with those which occur when butter is spread with a knife.

The effect of temperature over the range 6–18° C. on the hardness and structural viscosity of a number of butter samples has been investigated. The effect of reworking has also been studied.

An investigation of the effect of type of pasteurizer, rate of cooling after pasteurization, temperature during holding and during churning, temperature of wash water and amount of working showed that of these factors the only one which had any marked and consistent effect on the hardness of the butter was the rate of cooling of cream after pasteurization, rapidly cooled cream yielding harder butter. The use of low temperature wash water tended to reduce the hardness of the butter but the effect was small. The other factors had no consistent effect on the hardness of the butter.

1. Hydroquinone is an effective antioxidant for the butter-fat of spray-dried whole-milk powder, but in a concentration equivalent to 0·5% of the weight of fat (0·12% on the weight of powder) it produces an objectionable ‘metallic’ flavour in the powder and reconstituted milk.

2. Oat flour is much less efficient than hydroquinone as an antioxidant but 0·25% added to the milk, preferably before condensing, increases the resistance of the resultant powder to the development of tallowiness by the equivalent of about 4 months at normal temperatures. Raising the concentration of oat flour to 0·5% approximately doubles this increase but at the same time imparts a noticeable oat flavour to the powder.