586 Experiment station record. 



change in the amount of soluble proteids, which leads the author to 

 conclude that the change in the casein is not due to the action of the 

 lactic acid produced in the fermentation. He reaffirms his former 

 belief that the ripening of cheese is due largely and perhaps entirely to 

 the action of lactic acid bacteria. 



In the second paper the results of further experiments are reported. 

 Cultures were made in skim milk as before, inoculating the milk with 

 a mixture of one of the lactic acid bacteria formerly used isolated from 

 ripening cheese. At the end of 4 weeks it was found that while the 

 fresh filtered skim milk contained 033 per cent of nitrogen, the filtrate 

 from the culture contained 0.156 per cent, " showing again that a part 

 of the casein of the milk had been changed to soluble form." A chem- 

 ical examination of the filtrate from the culture showed that the soluble 

 proteids were for the most part in the form of amid nitrogen. 



The author compares the extent of the change in the casein noticed 

 by him in milk with that found by Bondzynski in Emmenthaler cheese, 

 indicating that the change was somewhat greater in the case of the 

 skim milk. 



In conclusion the author says that considering that practically only 

 lactic-acid-producing microorganisms are found in ripening cheese and 

 that other bacteria, as tyrothrix, etc., occur only in numbers too small 

 to mention, and furthermore that it has been shown that these lactic 

 acid bacteria are able to decompose and dissolve the casein, it can hardly 

 be doubted that these lactic acid bacteria are the cause of the ripening 

 of hard cheese. 



[The reason for the change in the casein noted in these experiments 

 and attributed to lactic acid bacteria, whereas no change has been 

 observed by other investigators when pasteurized milk was used, is 

 probably to be found in the enzym recently discovered by Babcock and 

 Russell to be a normal constituent of milk (see E. S. E., 9, p. 205). — Ed.] 



The rise and fall of bacteria in Cheddar cheese, II. L. Bussell 

 ( Wisconsin Sta. Rpt. 1896, pp. 95-111, pi. 1, fig. J).— The methods of 

 bacteriological analysis are described, especially those used in the 

 investigations on cheese, which are given iu considerable detail. In 

 order to bring the sample of cheese into a finely divided state so that 

 bacteria can develop, the cheese is triturated in a sterile mortar in 

 contact with sand or sugar. It is then added to a known volume of 

 sterile water and thoroughly shaken, which dissolves the sugar, leaving 

 the bacteria in suspension in the emulsion of casein, fit, and water. 

 Culture plates are made by adding to the gelatin 1, 2, or 3 drops of the 

 cheese mixture by means of a pipette. 



The results are tabulated of determinations of the number of bac- 

 teria per gram in 6 different Cheddar cheeses at different stages of the 

 ripening process; and the number of those producing lactic acid and 

 gas, digesting casein, and inert bacteria are given. These data are 

 discussed at length and are shown graphically. 



