1014 EXPERIMENT STATION RECORD. 



experiments concerning the relative development of these types in market, milk at 

 temperatures ranging from 1 to 37° C. are reported in detail. Some general conclu- 

 sions are drawn from the results of the present and earlier investigations (E. S. R., 

 15, p. 909). 



The development of different types of bacteria in ordinary market milk is believed 

 to be closely associated with temperature. The initial period, in which there is no 

 increase in the total number of bacteria, is very short when the milk is kept at 37° 

 ('., but may be 6 to 8 days when the milk is kept at 1°. Following this period the 

 bacterial content of the milk shows great diversity, depending upon the temperature. 



At 20° the ordinary lactic-acid bacteria develop rapidly and at the end of about 

 40 hours, when the milk becomes curdled, Bacillus acidi lactici constitutes commonly 

 over 90 per cent of the total number of bacteria. At this temperature other species 

 are almost completely held in check by the lactic-acid bacteria. 



At 37° the results are quite different. B. lords aerogenes commonly predominates 

 over B. acidi lactici. 1>. colt communis when present also grows rapidly. 



At 10° all types of bacteria develop somewhat uniformly after the first 2 or 3 days, 

 none of the lactic-acid types being favored. Neutral bacteria usually grow rapidly 

 and liquefiers often become abundant. This temperature is not so favorable for the 

 development of the lactic-acid bacteria as 20°. As the growth of other species of 

 bacteria at this temperature is less retarded, the wholesomeness of the milk is more 

 under suspicion. Except as regards the rapidity of bacterial growth there is but 

 little difference between 10° and 1°. 



"Milk is nut necessarily wholesome because it is sweet, especially if it has been 

 kept at low temperatures. At the temperature of an ice chest milk may remain 

 sweet for a long time and yet contain enormous numbers of bacteria, among which 

 are species more likely to be unwholesome than those that develop at 20°. From 

 this standpoint the suggestion arises that instances of ice-cream poisoning are per- 

 haps due to the preservation of cream for several days at a low temperature, such 

 treatment keeping the milk sweet, but favoring the development of species of bac- 

 teria that are, at higher temperatures, checked by the lactic organisms." 



The so-called " germicidal property" of milk, \V. A. Stocking, Jr. {< 'onnecti- 

 cut Shurs sin. h'/ii. 1904, pp. 89-106). — Experimental work is reported and conclusions 

 are drawn which coincide with those previously noted (E. S. R., 15, p. 185). It is 

 believed that "the decrease in the numbers of bacteria during the first few hours is 

 not the result of any 'germicidal condition or property' possessed by the milk, but 

 simply of the natural dropping out of those species which do not rind the milk a 

 suitable medium in which to develop." Typical lactic-acid bacteria are stated to 

 multiply continuously from the outset. 



Associative action of bacteria on the souring of milk, C. E. Marshall 

 {Science, v. sit., ;// {1905), No. 535, p. 492)- — A proteolytic bacillus isolated from 

 milk but not yet described, when associated with Bacillus acidi lactici increased the 

 acidity and hastened the curdling of milk over lactic-acid bacteria alone. The lactic- 

 acid bacteria developed more rapidly when associated with the proteolytic bacteria 

 than when grown in pure cultures. The products of the proteolytic bacteria exerted 

 the same influence as the presence of the living organism. A detailed account of the 

 work, including a description of the proteolytic bacillus, is to be published soon. 



On the formation of volatile alkaloids in sterilized skim milk by Bacillus 

 nobilis and the occurrence of such compounds in Emmenthal cheese, 

 L. Adametz and T. Chszaszcz {Oestevr. Mull:. //;/., 12 (1905), Nos. 3, pp. 35, 36; 4, 

 pp. 50, 51; 5, pp. 62, 63). — From skim-milk cultures of Bacillus nobilis 22 months old 

 the authors isolated a white, crystalline, odoriferous substance which proved to be a 

 volatile alkaloid easily soluble in alcohol, ether, and dilute acids, difficultly soluble 

 in water at ordinary temperature, and insoluble in concentrated sodium and potas- 

 sium hydroxids. A molecular rearrangement was brought about by the use of 



