with a wet cloth, these bacteria were prevented from falling into the pail, 

 as germs are unable to leave a moist surface. 



The cows drank from a wooden trough in the pasture field, and, on 

 examination, this water was shown to contain gas-producing organisms 

 which probably came from the soil, as the water obtained from the tap 

 was remarkably pure, containing less than 20 bacteria per c.c. and none 

 of these gas-producing forms. 



By washing out clean, dry cans which had been cleaned in the ordin- 

 ary manner with sterilized water, we obtained gas-producing bacteria. 



Very many flies were present in the stable, and these frequently fell 

 into the pail and added undesirable bacteria, which find in milk a good 

 food for growth. A number of these flies were captured, and single flies 

 were placed in test tubes containing a measured quantity of sterilized 

 water and well shaken. This water on analysis was found to contain 

 large numbers of gas-producing bacteria. Frequently, 50,000 bacteria 

 were obtained from a single fly, and of these over 20,000 were gas- 

 producing bacteria. 



Large numbers of gas-producing bacteria were also obtained from 

 manure. The ratio of gas-producing germs to other species in some IT 

 examinations was as 250 to 1. Cultures in sterilized milk made from 

 some of these bacteria gave the peculiar odor known to cheesemakers as 

 "gassy" milk, and others gave a characteristic "cowy" odor, although 

 this peculiar smell has usually been ascribed to stable odors. 



To summarize, gas-producing bacteria were found to be occasionally 

 present (1) in the udders of certain cows, (2) on the hairy coat of the ani- 

 mal, (3) in clean, dry milk cans, (4) in the watering trough, (5) from flies, 

 and (6) from manure. From these various locations, the gas-producing 

 bacteria may contaminate the milk. 



The gas-producing bacteria were readily killed by an exposure to 

 temperatures ranging from 137 degrees to 146 degrees F. for 10 minutes. 

 They were all l:il1cd by immersion in a 2 per cent, ammonia washing pow- 

 d'jr solution al 1-JO degrees F. and also in a 2 per cent, soda solution at 140 

 dcrees F. for 10 minutes. These soda and ammonia washing powders are 

 scarcely more effective than hot water for the destruction of these bac- 

 teria, but these substances aid in washing by helping to remove the dirt. 



By continued growth in milk it was found that these gas-producing 

 bacteria increased their power of fermenting the milk sugar. Thus, one 

 variety, which originallv produced 26 per cent, of gas, after growing for 

 some time in milk produced 62 per cent. ; hence those bacteria which 

 were not killed bv the hot water used in washing the cans would be more 

 liable to produce larger quantities of gas than those which came in from 

 other sources. 



[4] 



