1. With the assistance of the Central Council of Milk Recording Societies of England and Wales and its affiliated Societies, particulars were obtained of the calf losses, pre-natal and post-natal, sustained in 1936–7 by 315 herds situated in different counties of England and Wales. Further data were collected from twenty private owners in England and from forty-seven herds in a limited area in Scotland.

2. The herds in England and Wales were chosen in such a way as to give a fair representation of the geographical distribution of the cow population throughout the country. It is obvious, however, that they are a selected sample in which a relatively high standard of husbandry might be expected to prevail and their rates of mortality, therefore, will probably be below that of the general run of herds.

3. Owing to the early disposal of bull calves the losses of males after the first week of life are likely to be considerably understated. It is, therefore, wise to confine attention mainly to the figures for females.

4. In the 335 herds of England and Wales 12,544 female calves were born and of these 693, or 5°5 %, died before the age of 6 months.

5. Of 26,440 total births reported in England and Wales, 1231, or 4°4 %, were of stillborn animals.

1. The microflora of A.I.V. silage consists mainly of lactic acid bacteria—lactobacilli, streptococci, micrococci and sarcinae. Some samples also contain yeasts and yeast-like organisms.

2. Among the lactobacilli, both homo- and heterofermentative types are represented. The former include strains of Lactobacillus plantarum (Orla- Jensen) Bergey et. al.; in the heterofermentative group L. brevis (Orla-Jensen) Bergey et al. has been found.

3. Cultures of a motile homofermentative lactobacillus were isolated; this appears to be a new type. Among the unidentified heterofermentative lactobacilli, forms which may prove to be similar to the inactive group of Pederson were encountered.

4. The homofermentative streptococci were found to belong to the Streptococcus lactis group; the heterofermentative forms were identified with Leuconostoc mesenteroides (Cienkowski) van Tieghem.

5. Strains of unidentified homofermentative micrococci and sarcinae were isolated and shown to possess characteristics not usually associated with organisms of these types.

6. Streptococci, micrococci and motile lactobacilli were found mainly in fodder recently ensiled; the majority of the lactobacilli and sarcinae were associated with the older samples.

7. The characteristics which proved to be most valuable for the differentiations of the organisms were ability to produce carbon dioxide, percentage of lactic acid formed and lactic-acetic acid ratio.

The question whether the tomato pigment, lycopene, an isomer of carotene, can pass from food into milk in the cow has been submitted to direct test by feeding three different cows with tomato purée and examining the resulting milk fats separately for lycopene. No evidence of the presence of lycopene has been detected in the unsaponifiable matter of the butter fat when this was subjected to careful chromatographic adsorption and it is concluded that, although the cow normally absorbs α- and β-carotene and certain oxidation products of these substances from its food it completely excludes the isomeric and very similar lycopene which has been found in the faeces in considerable quantity after tomato feeding. The mechanism of this selective absorption of one isomer only is quite obscure.

2. Adsorption of the carotenoids of several colostrum fats gave no indication of the presence of lycopene but the adsorption columns contained two small zones above that of β-carotene due to traces of pigments having absorption maxima at 452 and 425 mμ. (petroleum ether b.p. 70–80°). These may be due to oxidation products of β-carotene.

1. A review of the literature shows that the destruction of living microorganisms by heat is a complex process, and that the problem is particularly difficult when it is applied to the heat resistance of spores.

2. The problems involved in the method of heating and in the choice of a container for the inoculated substrate for heat-resistance tests are discussed, with special reference to the difficulties encountered at high temperatures such as are used in studies with spores of aerobic bacteria. Four different types of containers, namely, (a) glass capillary tubes, (b) glass ampoules or bulbs, (c) glass Pasteur pipettes and (d) corked test tubes, have been tested, and the latter were found to fulfil the necessary requirements.

3. A trial test of the heat resistance was conducted on nearly forty strains of aerobic sporeformers isolated from canned milk products, in order to obtain general information regarding the difficulties which might be expected in later and more detailed studies. Many of the strains were found to be exceedingly heat resistant. No dormancy was apparent when the spores were heated and subsequently incubated in milk products. “Skips” were only observed to any great extent among strains of B. licheniformis.

4. Special studies of the heat resistance of three strains of B. subtilis which had produced bitterness and thinning in canned cream were made. Details are given of the methods of preparing spore suspensions for these tests and of preparing the substrates for subsequent inoculation in such a way that equal concentrations of spores are present in the final subsamples.

5. The effect of the reaction of the substrate on the destruction of two of these strains of B. subtilis by heat has been examined, but over the narrow range of pH. tested the results, which have been expressed as survival percentages, lack consistency.

A comparison of the value of various milk sera for the determination of the soluble phosphate and calcium of milk, using dialysis at 0–5° C. as a standard method, gave the following results:

(i) Rennet whey was the most satisfactory; with fresh milk it yields fairly accurate values for calcium, slightly low (average 5 %) for phosphate. With increasing acidity of the milk both sets of values tend to rise somewhat relatively to those of the dialysate, phosphate approaching the true value and calcium rising slightly above it.

(ii) Mercuric chloride borax serum gives high results for the soluble phosphate of fresh milk With increasing acidity of the milk, the results fall steadily.

(iii) Papain whey gives somewhat low results for both the phosphate and calcium of raw and pasteurized milk, with the same tendency as rennet whey to yield higher and improved results as the acidity of the milk: increases. With boiled milk it gives abnormally high results for both constituents. The additional phosphate and calcium appear to arise from the solution of colloidal calcium phosphate.

Milk of normal appearance from cows having a latent infection with Str. agalactiae yielded definitely less cheese than that from normal cows. Milk from cows free from “agalactiae” infection, yet classed as “abnormal”, behaved similarly. The lowered yield appeared to result from the lower casein and solids-not-fat contents of these “mastitis” milks.

With a single exception, the cheese made from these “mastitis” milks were not inferior in quality to those made from normal milks.

The pH of cheese at 14 days old appears to be the most useful means of measuring the extent of acid development in the cheese, and shows a very fair agreement with the observations of graders on mature cheese. Cheese with a pH value close to 4°90 at 14 days gained the highest average score at maturity.

Measurements of titratable acidity either on the aqueous extract of the cheese or directly on a paste of the cheese, readily distinguish cheese which are insufficiently acid, but do not clearly distinguish over-acid cheese or cheese of low pH value: The direct method of acidity titration has the disadvantage that the results are affected to such an extent by the colour of the cheese as to make impossible the comparison of results on cheese of different colour intensities.

pH or titratable acidity values for mature cheese are less useful indicators of the quality of the mature cheese than the values at 14 days.

In the milk of herds “free” from streptococcus infection, the presence of staphylococci has been shown to accompany chemical changes in the composition and abnormalities of pH.

In mastitis control schemes, based on Str. agalactiae infection, cases of staphylococcus infection are missed because of suppression of growth on the routine crystal violet blood agar of Edwards. Further, as clinical cases of staphylococcus mastitis causing serious disturbance are comparatively rare, the subclinical type may be present to a considerable extent and yet remain unsuspected. Thus in herds free from streptococcus mastitis, we have found that in 428 “cowtests” staphylococci werefound in 21 %. No clinical case was observed, although careful records of all abnormalities of udders and milks were kept.

The data which we have obtained show that staphylococcus infection accompanies changes of chemical composition which may be of importance in the preparation of milk products, but before categorical statements can be made more observations are obviously necessary.