An improved method for the determination of fat-globule size distribution has been worked out and applied to samples of sow's milk drawn sequentially. The distribution patterns for the globule sizes of sow's milk have been determined. Globules range in size from less than ½μ to over 7μ. The maximum number of globules occurs at different sizes in different sows, the largest maximum size group so far recorded being 2–2·5μ, the smallest maximum group being 0–0·5μ. There is no marked trend in size with stage of milking, though usually the maximum size is less for later milkings if it changes.

The strippings of sow's milk, unlike those of the cow, do not appear to be richer in fat than the earlier milk. Also unlike the cow, the globules of sow's milk do not cluster or clump (see Fig. 1). This explains the slow rate of creaming of sow's milk.

1. The present work was planned to provide an explanation of the lack of correlation for individual samples between the results of dye-reduction tests at 37·5° C. and keeping-quality tests at 22° C. A special study was made of the particular part played by the staphylococci (in thirty-eight samples) and the coli-aerogenes group (in thirty-seven samples) in dye reduction at 37·5° C. and in keeping quality at 22° C. A detailed study was also made of the changes in bacterial flora of twelve samples during incubation at these temperatures.

2. In milk, after overnight storage at 14° C., staphylococci were found to constitute only a small proportion of the bacterial flora, but their numbers increased during incubation at 37·5° C. (for the dye-reduction test) and at 22° C. (for the clot-on-boiling test). At the time of dye reduction staphylococci were found to constitute a major part of the bacterial flora, particularly in samples taking 5 hr. or more to reduce the dye. Although the staphylococci increased in numbers during incubation at 22° C. they constituted only a relatively small proportion of the flora at the time of the end-point of the clot-on-boiling test.

3. Initially the coli-aerogenes group were found to constitute only a small proportion of the total bacterial flora. Some growth usually occurred during incubation at 37·5 and 22° C.

The corynebacteria that were isolated by non-selective methods from raw and pasteurized milk are of two main types: (1) heat-sensitive diphtheroid organisms which appear to be derived principally from the animal body, and (2) thermoduric saprophytes originating from dairy equipment. The characters of group (2), which are discussed in detail, indicate that all the cultures examined belong to a single species, Corynebacterium lacticum. Reasons are given for classifying that species in Corynebacterium and for suppressing the genus Microbacterium.

1. Attempts to produce in rabbits group N sera for Streptococcus cremoris, using suspensions of living, disintegrated and heat-treated bacterial cells, yielded only non-specific products, cross-reactions occurring most commonly and intensively with HCl extracts of the streptococci of groups K and L.

2. The non-specific antibodies in these sera were completely removed by absorption with streptococci of group K or L, the group N reactions being only partially impaired.

3. In order to inactivate, before immunizing rabbits, that antigen in the ‘cremoris’ cells responsible for stimulating the production of non-specific antibodies, the organisms were ‘absorbed’ with an excess of group K or L antiserum.

4. With suspensions of organisms treated in this way, potent group N specific precipitating sera were obtained for both freshly isolated and freeze-dried strains of Str. cremoris.

5. The identity of Str. cremoris with serological group N is thus established.

Streptococcus diacetilactis, isolated from spontaneously soured potato mash, was first described by Matuszewski, Pijanowski and Supińska in 1936(3). Its essential features included the production of large amounts of lactic acid and volatile products (including diacetyl), and it differed from the ‘lactis-cremoris’ group primarily in the production of carbon dioxide in milk, the utilization of citrate and in its vegetable origin. More recently, in his investigation of certain diacetyl-producing and citric acid-fermenting streptococci from milk and from starter cultures, Swartling(5) showed that strains which resembled closely the Str. diacetilactis of Matuszewski et al. belonged to serological group N. In an addendum to his paper, Swartling states that this observation has been confirmed by me with a freshly isolated strain of Str. diacetilactis (no. 2) received from Prof. Pijanowski and Dr Supińska the purpose of this Note is to record the experimental evidence for that statement.

During the twelve years from 1935 to 1946 the type of foods given to sixty-one Dairy Shorthorn first calvers during the months of February and March changed so that the dry-matter intake of the cows rose and the dietary fat fell, but there was little change in the Protein and Starch equivalent they received.

Milk yield varied directly with the amount of fat and starch equivalent in the diet and inversely with the dry matter.

The solids-not-fat percentage of milk varied directly with the amount of starch equivalent, and inversely with the dry matter content, of the diet.

The milk-fat percentage was not influenced by the foods given.

It was shown that the fall in the level of solids-not-fat in the milk was largely due to the increase in the dry matter intake of the cows.

1. The failure of clostridia to produce a butyric acid fermentation, when known to be present in Swiss-type cheese, is discussed.

2. It is suggested that inhibitory substances produced by the predominating lactic flora of young cheese are partly responsible for the suppression of the fermentation.

3. Details are given of the techniques used to investigate this supposition.

4. The evidence was obtained by examining fifty-one samples of Gruyère cheese, 78% of which were contaminated with clostridia. 85% of the samples contained inhibitory lactobacilli.

5. In 30% of the samples the inhibitory phenomena were sufficiently marked to give clear zones of inhibition against Staphylococcus aureus when a suspension of cheese was placed in penicillin cups.

6. Inhibition of Clostridium butyricum was demonstrated with pure cultures of lactobacilli. The cultures could grow at temperatures from 30 to 50° C, but were inhibitory only at certain temperatures of incubation which appear to be a strain characteristic.

7. The inhibitory substance(s) concerned is not nisin because it is acid and heat labile.

La formation de gaz dans la pâte du fromage fondu, au cours de la conservation, représente un défaut assez fréquent qui entraîne le gonflement ou même l'éclatement des emballages, notamment lorsque ces derniers sont constitués par des boites métalliques.

1. Hard cheese of Cheddar, Derby and Manfis types was made from cows' milk and from buffaloes' milk. Buffaloes' milk curd of the Derby type was also milled at different acidities.

2. Initial acidity was higher and rate of acid development was greater in cows' milk and curd, whilst loss of fat in the whey was lower.

3. Cows' milk cheese contained more moisture, more total, soluble, and non-protein nitrogen, but less fat than buffaloes' milk cheese.

4. During ripening, the rate of acid development and protein degradation was greater in cows' milk cheese, whilst loss of moisture was usually smaller.

5. Buffaloes' milk cheese was inferior in grading quality to cows' milk cheese.

6. Attempts to improve the quality of buffaloes' milk cheese were made by altering the Derby cheese-making process as follows:

(a) ripening milk longer before renneting;

(b) modification of the milk casein/fat ratio;

(c) combining (a) and (b);

(d) modification of the casein/fat ratio plus scalding of the curd at a lower temperature and for a shorter time.

7. The last treatment (d) proved most effective and yielded cheese of very similar chemical composition and grading quality to that obtained from cows' milk.

1. It has been shown that the biological value of undeteriorated dried skim milk is depressed to the same extent by the addition of 1·25% L-lysine as by the addition of 1·25% D-lysine. The latter is not used by the rat. It is therefore concluded that the added L-lysine is surplus to the animal's needs and that the apparent lowering of the biological value is due to excretion of the lysine in the urine.

2. The slightly greater loss in the biological value of milk stored in air-pack compared with gas-pack was eliminated by the addition of 0·5% L-histidine to the former. Histidine is not a limiting amino-acid in the control or stored gas-pack milks for either young or adult rats.

3. A lower biological value was found for the control milk with adult than with young rats at 4 and 8% levels of intake. No further lowering in the biological value of the stored milk, deficient in lysine, was observed with adult rats, the value obtained for this milk being independent of the age of the rat. These results are in keeping with the known lowered requirements of the adult rat for lysine.

4. The significance of these findings in relation to the known amino-acid requirements of young and adult rats is discussed.