Contamination of Mi 



favor of some of the cans being contaminated and thus in- 

 fecting the milk supply of the patrons. If the organism 

 is endowed with spores so that it can withstand unfavor- 

 able conditions, this taint may be spread from patron to 

 patron simply through the infection of the vessels that are 

 used in the transportation of the by-products. Connellhas 

 reported just such a case in a Canadian cheese factory where 

 an outbreak of slimy milk was traced to infected whey vats. 

 Quite a number of epidemics of typhoid fever have been 

 shown to have been disseminated in this way, and in Den- 

 mark and Germany with foot and mouth disease and tuber- 

 culosis, the danger is so great as to make it necessary to 

 heat all by-products taken back to the farm. 1 



Pollution of cans from whey vats. The danger is greater 

 in cheese factories than in creameries, for whey usually 

 represents a more advanced stage of fermentation than 

 skim-milk. The higher temperature at which it is drawn 

 facilitates more rapid bacterial growth, and the conditions 

 under which it is stored in many factories contribute to the 

 ease with which fermentative changes can go on in it. 

 Often this by-product is stored in wooden cisterns or tanks, 

 situated below ground, where it becomes impossible to 

 clean them out thoroughly. A custom that is almost uni- 

 versally followed in the Swiss cheese factories, here in this 

 country, as in Switzerland, is fully as reprehensible as any 



1 Storch (40 Kept. Danish Expt. Stat., Copenhagen, 1898) has devised a test 

 whereby it can be determined whether this treatment has been carried out or 

 not: Milk contains a soluble enzym known as galactase which has the property 

 of decomposing hydrogen peroxid. If milk is heated to 176 F. (80 C.) or above, 

 this enzym is destroyed so that the above reaction w> longer takes place. If 

 potassium iodid and starch are added to unheated milk and the same treated 

 with hydrogen peroxid, the decomposition of the latter agent releases oxygen 

 which acts on the potassium salt, which in turn gives off free iodine that turns 

 the starch blue. 



