206 DOMESTIC ANIMALS, DAIRYING, ETC. 



by a capsule of a sticky, gummy substance. This gum or slime holds 

 the bacteria together. When a thread is drawn out it is really a chain 

 of bacteria held together by their sticky capsules. 



Ropy milk is, so far as known, in no way detrimental to health. 

 The famous Edam cheeses are nearly all made from milk which has 

 undergone this fermentation. The peasants of Norway consider 

 ropy milk a desirable beverage and bring about this fermentation 

 by adding to fresh milk the leaves of certain plants on which the 

 bacteria causing ropy milk are abundant. Most people, however, 

 object seriously to milk with any tendency to form threads. This 

 trouble frequently affects the milk of a dairy day after day and is 

 removed only by the most drastic measures. 



Outbreaks of this nature frequently occur in the cold months, 

 because the bacteria of this group thrive better at low temperatures 

 than the lactic-acid bacteria which hold them in check under normal 

 conditions. In one case it was found that these bacteria were abun- 

 dant in the dust of the stable. The trouble was removed by a thor- 

 ough cleaning and whitewashing. In another serious and persistent 

 outbreak it was found that the milk as it came from the dairy con- 

 tained few or no ropy milk bacteria, but that they were abundant 

 in the water tank in which the milk was held over night. The small 

 amount of water occasionally splashed into the cans added sufficient 

 bacteria to make the milk ropy in a comparatively short time. The 

 utensils and floor had become so thoroughly impregnated with this 

 organism that milk exposed in the room or strained through the 

 wire strainer became ropy without contamination with the water. 

 The trouble w r as removed by thoroughly scalding all the utensils, 

 disinfecting the floor with a 5 per cent sulphuric acid solution, and 

 destroying the organisms in the ice water by adding potassium 

 bichromate. This was used in the proportion of 1 part in 1,000, 

 or, roughly, 1 ounce to 1 cubic foot of water. 



The source of the trouble can sometimes be easily located by 

 taking small samples of the milk in clean glass jars at different 

 stages in the handling. These should be covered, set away in a cool 

 place to retard the souring, and examined after twenty-four to thirty- 

 six hours for indications of ropiness. 



In dairies getting milk from a number of farms the source of 

 the difficulty may be located on some particular farm and proper 

 methods taken to remove the source of contamination. 



Any precaution is almost sure to be ineffectual if all utensils 

 coming in contact with the milk are not thoroughly scalded, or, 

 better still, steamed. 



Miscellaneous Fermentations, In addition to the various fer- 

 mentations previously described, milk may undergo many other 

 changes as a result of the action of bacteria or other micro-organ- 

 isms. The color may be changed. The appearance of color in milk 

 is due to the growth of bacteria which produce a pigment soluble 

 in water. All the colors of the rainbow, from bright red to violet, 

 are formed by bacteria. Blue milk, which is the most common of 

 the color fermentations, is probably due to contaminations from 



