224 Bulletin 158. 



In the investigation, it seemed best to begin with the 

 "gassy " and tainted curd to find if possible the specific cause, 

 and then to look for its source. Without entering into the 

 technicalities of the methods followed, the results of a careful 

 bacteriologic examination of the curd showed that both the taint 

 and the gas were caused by the same species of gas producing 

 bacteria, a microorganism resembling very closely, if not iden- 

 tical with, Bacillus coli communis. The evidence of the correct- 

 ness of this assertion is based entirely on the fact that when 

 cheese was made with milk which had been sterilized and then 

 inoculated with this bacillus, that the "gassy" curd and the 

 taint in question would develop. 



The factory itself was kept scrupulously^ clean and the only 

 possible source for the organism there seemed to be in the ren- 

 net or in the water used in cleaning the vats. These were both 

 subjected to a thorough bacteriologic test for gas producing bac- 

 teria with negative results. This outcome practically eliminated, 

 as was expected, all suspicion that the organism came from the 

 factory. It was then determined by making the milk up sep-. 

 arately from the two dairies that the bacillus which was causing 

 the trouble came to the factory in the milk from the dairy on the 

 farm. It remained to be found whether its presence in the mixed 

 milk was due to the dust and filth which invariably fall into the 

 pail from the flanks and udder of the cows at each milking, or, 

 whether it was in the milk ducts themselves, and if so to deter- 

 mine which cows were thus infected. 



Cheese was made at our suggestion leaving out the milk of the 

 cows which were reported to have suffered from the retained 

 placenta without, however, any improvement in the condition of 

 the curd. This necessitated a careful examination of the milk 

 from each cow in the dairy. This was made from a series of 

 samples taken daily for a period of two weeks. 



The bacteriologic examination consisted in testing for gas pro- 

 ducing bacteria, using the fermentation tubes and also the curd 

 test recommended by Russell of the Wisconsin Agricultural 



