92 Dairy Bacteriology. 



140 F. is that the natural creaming is practically unaf- 

 fected. Of course, where a higher ternperatu re is employed, 

 the period of exposure may be materially lessened. If 

 milk is momentarily heated to 185 F., it is sufficient to 

 destroy the vitality of the tubercle bacillus. This is the 

 plan practiced in Denmark where all skim milk and whey 

 must be heated to this temperature before it can be taken 

 back to the farm, a plan which is designed to prevent the 

 dissemination of tuberculosis and foot and mouth disease 

 by means of the mixed creamery by-products. This course 

 renders it possible to utilize with perfect safety, for milk 

 supplies, the milk of herds reacting to the tuberculin test, 

 and as butter of the best quality can be made from cream 

 or milk heated to even high temperatures, 1 it thus becomes 

 possible to prevent with slight expense what would other- 

 wise entail a large loss. 



2. Dilution. Another method that has been suggested 

 for the treatment of this suspected milk is dilution with a 

 relatively large volume ot perfectly healthy milk. It is a 

 well known fact that to produce infection, it requires the 

 simultaneous introduction of a number of organisms, and 

 in the case of tuberculosis, especially that produced by in- 

 gestion, this number is thought to be considerable. Geb- 

 hardt 9 found that the milk of tuberculous cows, which was 

 virulent when injected by itself into animals, was innocuous 

 when diluted with 40 to 100 times its volume of healthy 

 milk. This fact is hardly to be relied upon in practice, un- 

 less the proportion of reacting to healthy cows is positively 

 known. 



It has also been claimed in the centrifugal separation of 



1 Practically all of the finest butter made in Denmark is made from cream that 

 has been pasteurized at temperatures varying from 160-185 e F. 

 Gebhardt, Virch. Arch., 1890, 119: 12. 



