1. As regards their nutritive value for milk production, the proteins of spring grass are markedly superior to those of autumn grass. This is shown not only from a study of milk yield, but from the increased excretion of N and S in the urine, the increased creatine excretion, and the lower biological value given by autumn grass.

2. A study of the N and S metabolism of cows receiving fresh and artificially dried grass fails to reveal any significant differences in the nutritive value as a result of artificial drying. There are no significant differences between the biological values of the proteins of fresh and of artificially dried autumn grass. A comparison of the mean biological values of the proteins of fresh and of artificially dried spring grass indicates that the latter has an inferior value for milk production, but the differences largely disappear when the biological values are calculated to a common standard.

The influence of mastitis and of Br. abortus infection, separately and combined, has been observed in two tuberculosis-free herds during the years 1929–31 and 1930–4 respectively. Actual abortions in these herds were few, but many cows were affected with Streptococcus mastitis in a subclinical form. The results, comprising the examination of 180 lactations in Ayrshires and 193 in Friesians, have been considered in relation to the results of others who have investigated the influence of Br. abortus infection on the yield.

When all the lactations of all cows were considered, the average reduction in yield per lactation was 954 lb. due to mastitis and 1685 lb. due to mastitis and abortion combined. Among the Ayrshires of one herd the average reduction due to mastitis was 892 lb.

1. The titration method for the estimation of colloidal tricalcium phosphate in milk was found to agree closely with the determination of total colloidal inorganic P2O5.

2. The method was used to study the solution of tricalcium phosphate in milks of rising acidities.

3. Close agreement was obtained between the actual increase in total P2O5 in the wheys of souring samples and that calculated from the disappearance of tricalcium phosphate as found by the titration method.

4. The discrepancy between the actual increase in whey calcium in such cases and that calculated from the titration figures was attributed to the solution of calcium from the calcium salt of caseinogen. From figures so obtained it would appear that colloidal calcium phosphate dissolves with greater ease in milk than the calcium of the protein salt.

5. A linear relationship was found to exist between the ordinary titration value of milk and the three other values used in this estimation, and also between the curd acidity and milk acidity.

6. Average figures are given for the tricalcium phosphate content of the samples studied and for the various titration factors.

1. Determinations have been made of lactose and lactic acid in whey, curd and curd juice throughout the cheese-making process.

2. The effect of adding salt to curd at various stages of the process on the concentration of lactose and lactic acid in the whey has been investigated.

3. The rate of penetration of salt into curd has been determined, and it has been shown that by the time the cheese is normally hooped but little salt has reached the centre of each curd strip. Within 12 hours after hooping the distribution of salt is substantially uniform.

4. It has been shown that the conversion of lactose to lactic acid by starter bacteria in the cheese vat is almost quantitative.

5. Evidence has been brought forward indicating the presence of bound water in cheese curd.

6. It has been shown that a Donnan equilibrium controls the partition of electrolytes between curd and whey.

Various types of proteolytic cocci, including several acid-proteolytic strains, have been isolated from foremilk and rennet extract (l) and subsequently from ripened Cheddar cheese. A study of the proteolytic activities of these cultures in milk forms the subject of this investigation.

Since the publication on physiological youth in bacteria by Sherman & Albus(1), many workers have demonstrated that the resistance of microorganisms to environmental changes is greatly influenced by the age or stage of growth of the organism under consideration.