+29. Inert types.+--As the name indicates, these are organisms not known to have an appreciable effect on milk. The ordinary tests fail to connect them with important processes; hence they appear to feed upon, but not to affect the milk in any serious way. Milk ordinarily contains more or less of these organisms, but no particular significance is attached to their presence. +30. Alkali-producing bacteria.+--This group of organisms has only recently been studied in relation to its action on milk. Investigators still disagree as to the usual percentage in the normal milk flora. Their presence in milk has been considered to be relatively unimportant. +31. Butyric fermenting types.+--Organisms causing butyric fermentation may be present in the milk, but seldom become active, because they are commonly anaërobic and so will not develop in milk kept under ordinary conditions, and the rapid growth of the lactic acid-forming bacteria prevents their growth. These organisms act on the milk-fat, decomposing it. Butyric acid fermentations are more common in old butter and cheese. In these, the fermentation causes a rancid flavor. +32. Molds and yeasts.+--The cattle feed and the air of the barn always contain considerable numbers of yeasts and mold spores. Yeasts have been found by Hastings[12] to cause an objectionable fermentation in Wisconsin cheese. No further study of this group as factors in cheese-handling has been reported. Mold spores, especially those of the blue or green molds (Penicillum sp.) and the black molds (Mucors), are always abundant in milk. These spores are carried into all cheeses made from unpasteurized milk, in numbers sufficient to cover the cheeses with mold if they are permitted to grow. Pasteurization[13] kills most of them. The border-line series commonly referred to as the streptothrix-actinomyces group are also very abundant in all forage and are carried in large numbers into all milk and its products. +33. Bacterial contamination of milk.+--When drawn from the cow, milk is seldom if ever sterile. Organisms usually work their way from the tip of the teat into the udder and multiply there. The fore milk usually contains more organisms than does that drawn later. Most of the bacterial contamination of the milk is due to the handling after it is drawn from the cow. +34. Germicidal effect of milk.+--Authorities agree that when a bacterial examination of the milk is made, hour by hour, beginning as soon as it is drawn from the cow, there is no increase in the number of organisms for a period of several hours at first, but an actual reduction not infrequently takes place. This is called the "germicidal"[14] property of milk. The lower the temperature of the milk, the longer and less pronounced is the germicidal action; the higher the temperature, the shorter and more pronounced is this action.