320 



SCIENCE 



[N. S. Vol. XLII. No. 1079 



Slimy and Eopy Milk: E. E. Buchanan and B. 



W. Hammee. 



A study of slimy and ropy milk sent for ex- 

 amination to the Dairy Bacteriological Labora- 

 tories of Iowa State College has shown the fol- 

 lowing: 



1. Cultures of organisms secured from slimy 

 starters, apparently typical Streptococcus lacticus 

 forms, sometimes showed marked capacity to pro- 

 duce ropinesa when inoculated into sterile milk. 



2. Associative action of organisms in some cases 

 is responsible for ropiness. 



3. Bacterium (lactis) viscosum is one common 

 cause of slimy mUk. 



4. Certain peptonizing bacteria, as Bad. pepto- 

 genes produce a very slimy residuum after diges- 

 tion of the casein. 



5. Bacterium hulgaricum and certain related 

 high acid organisms frequently produce marked 

 viscosity in milk. 



Sliminess in milk, therefore, is apparently due to 

 different causes with different organisms. 



Methods of control and prevention of slimy 

 milk are discussed. 



Descriptions of thirty-three species of bacteria 

 that have been found associated with milk are 

 given, and the literature reviewed. 

 Factors Influencing the Resistance of Lactic Acid 



Bacteria to Pasteurization: K. Peiser. 



In milk and cream pasteurized at 63° C. (145° 

 E.) for twenty minutes in a "Perfection" Pas- 

 teurizer (200 gal. capacity) were found a num- 

 ber of strains of the Bact. lactis acidi type whose 

 thermal death-point in broth is below the pas- 

 teurization temperature. 



The thermal death-point of a number of these 

 strains was determined in bouillon (10° acid to 

 phenolphtalein) and in boiled whole milk, sepa- 

 rated milk and milk serum, with the result that 

 the average thermal death-point is in whole milk 

 5° C, in separated milk 2.5° C, and in whey 

 0.5° C, higher than in bouillon. These results 

 indicate that the protection given to the sus- 

 pended lactic bacteria by the casein and coagu- 

 lated albumen of separated milk raised their ther- 

 mal death-point 2.5° C. and that the protein and 

 fat of whole milk raises their thermal death-point 

 5° C. In this we see a reason why some bacteria 

 whose thermal death-point is low are found in 

 pasteurized milk. 

 Bacteria in Preserved Eggs: Maud Mason Obst. 



Commercial and strictly fresh June eggs packed 

 in solutions of 1:5, 1: 10, 1 : 15, 1: 20 parts com- 

 mercial waterglass, and in saturated lime solutions 



were stored in laboratory, barn, cellar and at 

 34° F. Thermograph records were kept. Bac- 

 teriological and chemical examinations were made, 

 also cooking experiments and parcel-post shipments. 



Temperature of 80° F. in laboratory permitted 

 rapid multiplication of bacteria in eggs. 



Barn temperature varied from 10° F. to 87° F. 

 Eggs froze in solutions, later some thawed with- 

 out breaking and at end of experiment showed 

 no effects attributable to freezing. Bacterial con- 

 tent was uniform and fairly low. Bacterial in- 

 crease in commercial eggs in 1: 10 waterglass waa 

 rapid, especially in albumen, during first two 

 months of storage. 



Eggs stored in cellar held a uniformly low bac- 

 terial content throughout experiment. 



At 34° F. eggs showed exceptionally low 

 counts. 



Waterglass solutions contained practically no 

 bacteria per c.o. after five months of storage. 

 Average bacterial content of eggs in nearly every 

 lime solution increased more rapidly than in water- 

 glass, necessitating the discard of certain lime so- 

 lutions early in experiment. 



Curves were plotted showing increase of aver- 

 age bacterial content in relation to length of stor- 

 age. Bacterial content of albumen in most eases 

 remained lower or equal to that of yolks for 150 

 or 250 days of storage, then the former increased 

 markedly and generally far exceeded that of the 

 yolk. 



From good eggs were isolated: M. aurantiacus, 

 B. prodigiosus, B. subtilis, B. pyocyaneus, B. 

 fluorescens liquefaciens, B. termo, B. zopfi. One 

 decomposed egg contained B. proteus in large 

 numbers. 



Some Methods and Appliances Used in the Ele- 

 mentary Courses in Bacteriology: W. H. Wright 

 and E. G. Hastings. 

 A description of the laboratory equipment used 



with large classes. 



The Effect of Certain Organic Soil Constituents 



on the Fixation of Nitrogen by Aeotobacter: 



Bruce Williams. 



This paper reports a study on the effect of vari- 

 ous organic compounds on the growth of Azoto- 

 bacter. The compounds used were those likely to 

 be constituents of the soil. 



One liter Erlenmeyer flasks, to which were added 

 15 grams of pure sea sand, previously washed and 

 burned, afforded an excellent surface upon which 

 Azotobacter developed. To each of these flasks 

 was added 100 c.c. of Ashby's media. 



