:rAIRY FARMING DAIRYING. 987 



report an account is given of experiments made with a microcioccus originally isolated 

 from pasteurized milk, to determine if similar results could be obtained with other 

 bacteria and to ascertain why the destructii)u of l)acteria in milk is subject to such 

 variation. 



The thermal death point of the micrococcus with a 12-minute ex])osure in a sealed 

 tube was found to be about 76° C. The results were practically unif(jrm when 

 bouillon, skim milk, whey, and milk were used as media. In milk heated in an 

 oj)en vessel the micrococcus resisted a temperature of 80°. Milk drawn from 

 beneath the surface by a siphon was sterile, while numerous colonies developed on 

 plate cultures made from the surface membrane. The surface membrane on milk 

 heated at 80° was removed at the end of 10 minutes and showed the presence of 

 bacteria. A second membrane formed, which was removed at the end of another 

 period of 10 minutes and found to be sterile. The organism was not destroyed in the 

 film when the milk was heated for 20 minutes at the same temperature. 



The experiments show an increased resistance of the organism in the surface mem- 

 brane. Two possiljle explanations of this phenomenon were advanced, (1) a dimin- 

 ished temperature of the surface membrane as compared with the remainder of the 

 milk, and (2) protection afforded the bacteria by the membrane itself. The first 

 was disproved by removing the membrane and immersing it in water at the same 

 temperature. The second hypothesis is therefore considered the most probable 

 explanation. 



The ripening of cream, H. W. Conn and W. M. Esten {Connectlent Storrs Sta. 

 apt. 1900, pp. 13-33). — This article has already been noted from another source 

 (E. S. R., 13, p. 688). 



Investigations on the sources of the acid organisms concerned in the sour- 

 ing of milk, R. H. Burr [Coi)ihy:1lcut Starrs Sfa. Ej^t. 1900, pp. 06-81). — The bacteria 

 mainly concerned in the souring of milk and cream in Connecticut are Bacillus acidi 

 lactici, B. acidi lactici II, and B. Inctis aerogenes, of which the first is by far the most 

 important, comprising commonly 90 per cent of the organisms present in ripened 

 cream. Three series of experiments were conducted by the author at the Connecti- 

 cut Hospital for the Insane to determine the source of these organisms, especially 

 that of B. acidi lactici. 



In the first and second series of experiments made in 1900 and 1901, bacteriolog- 

 ical studies were made of tlie milk as drawn directly from 70 cows kept under excel- 

 lent dairy conditions. The results on the whole show that lactic acid bacteria are 

 not present in freshly drawn milk, but are a secondary contamination from some 

 external source. The acid organisms multiply rapidly, and soon check the growth 

 of the liquefying and other bacteria present in fresh milk. All 3 species of lactic 

 acid bacteria were found in the air and in the dust and dirt falling from the cows 

 during milking. The B. acidi lactici was present in the air in the smallest numbers. 



In the third series of experiments 2 cows reacting to tuberculin were slaugh- 

 tered and a Ijacteriological study was made of their udders. In both cases the 

 udders were ai)parently normal. None of the 3 species of bacteria was found. An 

 organism producing an acid reaction in milk without curdling was found in both 

 udders and is described. It is considered identical with the Micrococcus acidi lactici 

 of Conn and the micrococcus described by Ward (E. S. R., 12, p. 184). This 

 organism is not considered of any significance in the souring of milk. 



Starters, G. L. McKay {loiva Agriculturist, 1 {1902), No. S, pp. 5-7). — A brief 

 popular account of the use of pure cultures in the ripening of cream. 



Water in butter — an important feature, G. S. Thomson {Jour. Agr. and Ind. 

 South Austrnliii, .7 (190?), Xos. 0, pp. r>/,4-.)49; 8, pp. 678, 679). — The average water 

 content of over 50 sam[)les oi South Australian butter analyzed l)y the author was 

 11.7 per cent. The butter trier was found unreliable as a jiractical guide for judging 

 the amomit of water in butter. A difference of 1.4 i)cr cent in the water content of 

 butter followci] a difference of 4° K. in the tiMuperature of the cream when churned. 



