202 DOMESTIC ANIMALS, DAIRYING, ETC. 



mines largely tjie numbers that they carry. The average for 414 

 flies was about one and one-fourth millions bacteria on each. 

 (Conn. B. 51.) 



The Air. The air is not a source, but a medium, of distribu- 

 tion for bacteria. The outdoor air away from cities is very free 

 from organisms. It is the interiors of buildings where germs collect 

 that cause the air to become a medium of distribution. The con- 

 stant accumulation of dust that is not removed is ready at the 

 slightest commotion to be raised into the air and spreads itself to 

 every part of a room. After an hour or two it settles on all exposed 

 surfaces ready to be again wafted into the air at any disturbance. 

 'Dust and bacteria are almost synonymous terms. The former 

 scarcely ever exists without the latter. In fact, bacteria utilize float- 

 ing dust as air ships for distribution. Hay is the most abundant 

 source of dust and bacteria in a barn and stable. If the dust is 

 never removed it collects in very large quantities. Grain feeds are 

 dusty and well supplied with bacteria. Poor or swamp hay bed- 

 ding is a very abundant source of bacteria and is so near the milk 

 pail during milking that it furnishes large numbers that get into 

 the milk. It is advisable not to use hay for bedding, but instead 

 use sawdust, planer shavings or clean straw. Dry sweeping is the 

 worst method of cleaning floors, because it fills the air with dust 

 that settles over everything and only removes the coarser particles 

 of dirt. Dusting should be done with damp cloths, not dusters. 

 Sweeping with some damp material spread over the floor, or better, 

 on cement floors, flush with water. The air is, then, a medium for 

 the distribution of nearly all kinds of bacteria, including a few 

 varieties of disease germs whenever the sources of bacteria and dust 

 are dried and pulverized materials. (Conn. B. 51.) 



Lactic Fermentation. As pointed out in the previous bulletin, 

 the lactic fermentation is produced by a large variety of bacteria. 

 This fact has been confirmed over and over again in recent years 

 and the list of lactic-acid bacteria has been constantly growing. At 

 the present time a very large number of species (over one hundred) 

 have been described as producing the acid fermentation of milk. 

 To what extent, however, they are all to be regarded as producing 

 the lactic fermentation we can hardly say, because in most cases no 

 attempt has been made to determine chemically the presence of 

 lactic acid, the investigators being ordinarily content with the deter- 

 mination of the production of an acid reaction. Moreover, it is 

 impossible to state to what extent these different species are really 

 different from each other. The list includes many pathological 

 forms, as well as the distinctively dairy bacteria. The first-described 

 species, Bacillus acidi lactici, has been found to assume many 

 varieties. 



Eleetricity. The action of lactic organisms appears to be still 

 the only known method of spontaneous milk souring. It is true 

 that careful investigation has shown that when milk is drawn fresh 

 from the cow it is commonly very slightly acid, an acidity depend- 

 ent upon certain conditions in the milk gland, but no other second- 



