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1. The numbers ofStreptococcus bovisin the rumen of a heifer and a steer, each having a permanent rumen fistula, were shown to remain relatively constant within the range 105to 107per ml. rumen liquid (strained rumen contents) over a period of more than 3 years.2. The numbers ofStrep. boviswere little affected by the change in diet from stall-feeding (oats, beans, hay and straw) to grass or vice versa.3. There was a slight increase in the numbers ofStrep. bovisfollowing each meal when the animals were stall-fed, but no appreciable variation in numbers throughout the day when the animals were at grass.4.Strep. bovishas also been isolated from the rumen of freshly slaughtered cattle and sheep from different parts of the country, from the rumen of goats and calves and from the faeces of cattle, goats and in small numbers associated withStrep. equinusfrom horse dung.5.Strep. boviswas found in the contents of the omasum, large intestine and caecum of three cattle, but in the small intestine of only one of these animals. Very small numbers ofStrep. boviswere detected in the abomasal contents of only four of twelve animals examined.6. The characteristics of these strains ofStrep. bovishave been described. The synthesis of an iodophilic polysaccharide byStrep. bovishas been demonstrated.7. A possible role ofStrep. bovisin the decomposition of starch and other carbohydrates in the rumen is discussed.

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With 7 Figures)The survival of the microflora during the storage of dried milks has been shown (l) to vary considerably from sample to sample even when the bacteria appeared to be of similar types and the milks were dried in the same plant. The variation may have been due to differences in the moisture content of the dried milk, but no data were available with which to test this hypothesis. Preliminary experiments with three different types of milk powder showed that over the limited range of humidity used, the lower the relative humidity in which the milk powders were stored, the greater the survival of the bacteria contained in the powder. The scope of the investigation was then extended to cover a wider range of relative humidity and longer periods of storage. It was found that although in general the higher the humidity (or moisture content) the lower the survival rate of the microflora in the milk powder, survival was greater at 5-20 % relative humidity than at humidities above and below this level. A brief account of part of this work has been published elsewhere (2).The fact that survival was greatest at 15-25 % E.H. had been observed by Watts (3) for dried cultures of Streptococcus agalactiae. To determine whether this was a characteristic common to several types of bacteria the investigation was continued to include bacteria typical of the microflora of milk powders. Pure cultures of these bacteria in skim milk were dried and stored at varying relative humidities. Maximum survival was found at 5-20% R.H.Dried suspensions of bacterial spores have been shown to be markedly sensitive to the complete absence of humidity, although their viability was unaffected by exposure to 5 % R.H. for two years. METHODS Milk powdersWeighed portions of approximately 1 g. milk powder were spread in a thin layer in small Petri dishes (2 in. diam.) and placed in desiccators over aqueous sulphuric acid solutions of the specific gravities necessary to give the required relative humidities (4). The lids of the Petri dishes were raised slightly with small pieces of rubber tubing to allow free circulation of the air in the desiccator. At intervals two dishes were removed and immediately examined for moisture content and plate count. The moisture content was calculated as a percentage of the dry weight after heating at 100° C. for 3 hr.The plate count, after reconstitution at room temperature, was made on Yeastrel milk agar at 37° C. and was calculated per g. of fresh powder. The relative numbers of J. Dairy Research 20 5

SUMMARY: The bacterial colony count of raw milk and of milk powder using milk agar prepared from a proprietary brand of the dehydrated medium has been compared with that obtained using the fresh medium prepared in the laboratory. No significant difference was found in 17 milks which were examined using the roll‐tube technique and 8 replicates/medium but in a second series of 32 milks the plate count (3 replicates/medium) was significantly lower on the reconstituted than on the fresh medium. Some milk powders gave a much lower plate count on the reconstituted medium, due to the inability of the latter to support adequate growth of Streptococcus thermophilus.