1. The concentration of carotene and of vitamin A in colostrum and colostral fat and the total daily yield of these substances in successive milkings has been studied for four shorthorn cows and nine heifers.

2. The concentration of vitamin A in the first colostrum ranged from 8160 to 820 Moore blue units per 100 g. and that of carotene from 2026 to 411 Moore yellow units per 100 g.

3. The highest and lowest concentrations and yields of vitamin A and carotene respectively in samples of colostrum and later milk were in the ratios: per g. of colostrum (milk) 35:1 and 65:1; per g. of fat 27:1 and 34:1; calculated on daily yield 31:1 and 65:1. This last calculation favours colostrum.

4. Access to pasture before calving appeared to have no effect on the secretion of vitamin A in colostrum but increased the output of carotene.

Our best thanks are due to Mr A. G. Cotton who supervised the collection of the samples of colostrum and to Miss D. V. Dearden for churning the butters.

Data have been given of the variations in the calcium ion, ultrafiltrable calcium complex, non-ultrafiltrable calcium complex and protein-bound calcium at normal parturition in the dairy cow, and an interpretation of the results has been presented. The variations observed have been shown to be consistent for all the animals studied.

Serum phosphatase did not show any consistent changes at the time of parturition.

The following average fractionation of serum calcium in the dairy cow has been reported:

1. Three Shorthorn cows were grazed on the best available permanent pasture when the growth of grass was vigorous, and three other cows of similar lactational history continued to be stall-fed. At the time of the experiment they had been on winter rations for 6 months.

2. By suitable blending of morning and evening milkings the fat content of the milk from both groups of cows was adjusted daily to a common level. A part of each milk was then holder-pasteurized.

3. Four groups of specially prepared litter-mate male rats were fed ad lib., for a period of 8 weeks, on raw and pasteurized milks, both being supplemented with minerals. There were no differences in appetite or gain in weight.

4. In similar experiments sugar was added to the milks to double their caloric value. Again the growth and appetite of the animals were the same on the raw summer and “winter” milks. Pasteurization did not alter significantly the value of the milks, but the summer milk, whether raw or pasteurized, was superior to the pasteurized “winter” milk.

5. Guinea-pigs receiving the raw mineralized milks alone or with sugar died within a comparatively short time. There was no difference in growth performance or time of survival between the summer and “winter” milk groups.

6. These experiments give no indication of the presence of a specific new appetite or growth factor in pasture milk.

1. A description is given of a weakly haemolytic organism, which first appeared as a contaminant, in the form of pin-point colonies, in agar plates inoculated with dilutions of a cream which had been subjected to partial processing in a butter churn.

2. Though it resembled in many respects certain strains of Str. bovis recently isolated from pasteurized milk in America, it is concluded that the majority of its characteristics showed it to be a resistant strain of Str. thermophilus which had adapted itself to contaminate a churn.

3. That the churn was responsible for the spread and maintenance of this heat resistant contaminant is regarded as significant and indicates that efficient pasteurization must be followed by storing and processing in sanitary equipment.

I am indebted to Dr M. Grimes for his help and suggestions in the course of this work.

In order to compare the old and the modified methods of the methyleneblue reduction test, 185 samples of raw milk were examined. We followed Wilson's method absolutely, but included two tubes in each test, one of which was inverted and the other not.

The results obtained and their interpretation agreed with the theoretical expectations given in our previous paper, and briefly outlined at the beginning of the present paper.

It is found that the deviations in the reduction time, corresponding to a given initial number of cells, are smaller by the modified than by the old method, and that the average time of reduction is shorter.

The smaller variation in the reduction time corresponding to a given number of cells at the beginning of the test is due probably to a more uniform distribution of the bacteria in the milk following the inversion of the tube. Wilson's suggestion that the shortening of the reduction time in the modified method is due to the stimulation of bacterial growth proves to be entirely correct. We obtained the average coefficients of multiplication in the old method of 0·660, and in the modified of 0·885.

Our results confirm on the whole the positive value of the modification of the methylene-blue reduction test as suggested and worked out by Wilson.

1. The influence of temperature, pH, oxygen tension and yeast autolysate on the production of by-products and the ratios of by-products formed to sugar utilized and lactic acid produced in milk by the heterofermentative lactic acid streptococci has been investigated.

2. The total production of lactic acid is increased by anaerobic conditions and low temperature. The ratio of lactic acid formed to sugar utilized is increased by anaerobic conditions and the presence of chalk.

3. The total amount of acetic acid is higher in the presence of chalk, at the lower temperatures and in yeast milk, but is decreased by anaerobic conditions. The ratio of acetic acid both to sugar utilized and to lactic acid formed is smaller at lower temperatures, in the presence of “growth factors” and chalk and under anaerobic conditions.

4. The total alcohol production is higher when yeast or chalk is added to milk, under anaerobic conditions and at lower temperatures, and similarly the ratio of alcohol formed to sugar utilized and lactic acid produced is increased.

5. Hydrolysis of residual lactose occurred in all cultures of Str. citrovorus and with some of the other streptococci in cultures to which chalk had been added.

6. Although the heterofermentative lactic acid streptococci possess respiratory enzymes, these fail to suppress aerobic fermentation (i.e. the Pasteur effect is slight).

The times needed for the complete inactivation of bacteriophages for the lactic streptococci by several chemical disinfectants in various strengths were determined. The phage preparations, consisting essentially of whey, contained the usual amounts of protein and lactose, so that the results obtained must be considered applicable only under the defined conditions. Hydrogen and hydroxyl ions were found to inactivate phage when they were present in sufficient concentration but their effects between pH. values of 4 and 7 were negligible over several days at room temperature.

By far the most effective of the disinfectants were active chlorine and permanganate, which suggests that the inactivation of phage is most readily brought about by oxidation.

1. Fluorimetric tests applied to commercially pasteurized and commercially sterilized milk showed that in the former some 10% and in the latter up to 50% of vitamin B1 was destroyed in the course of the heat treatment.

2. Riboflavin withstood both treatments without loss.

3. These findings are in satisfactory agreement with the results of earlier biological tests.

1. The application of the colorimetric dilution method for the determination of pH values in cheesemaking is discussed and the necessary precautions for accuracy described.

2. Bromthymol blue is recommended for milk and whey of pH. > 5·8 and the B.D.H. 4460 indicator for whey of pH < 5·8.

3. Titratable acidities and pH values each afford an incomplete picture of the working of a curd. Together they afford a valuable indication of the normality or otherwise of the making process.

4. The buffer value of whey rises steadily during manufacture. The pH rises abruptly after salting, although the titratable acidity continues to increase.

5. The buffer value of whey is controlled chiefly by the rate of working but tends to be lower with pasteurized milk.

6. A diagrammatic method for summarizing the “behaviour of a vat” and for detecting abnormal working is described.

Lyphan paper M 25 can be used for pH measurements in milk and whey in the pK range 5·4—6·6. As a rule the error does not exceed 0·1 pH.

In very acid milk and whey (pH < 5·4) lyphan paper of the L series may be used. Generally the deviation does not exceed -0·2 pH. In alkaline milk and whey lyphan paper cannot be used.

In milk and whey from cows infected with mastitis M 25 may be used unless the pH exceeds 7.