96 THE BOOK OF BUTTER 



selection of sweet cream in making butter of good keep- 

 ing properties. 



70. Killing pathogenic micro-organisms in cream. 

 The two diseases most readily transmitted by butter are 

 typhoid and tuberculosis. Typhoid fever is a disease of 

 man. On the other hand, tuberculosis is common to 

 man and beast, which, together with its greater prevalence 

 and viability, makes it to be feared far more than typhoid. 

 The spread of tuberculosis by butter has been studied by 

 many investigators. The table on page 97 by Briscoe 

 and MacNeal l shows the results of the research on this 

 important subject up to 1908. 



It should be noted that the table shows that 13.2 

 per cent of the 1233 samples of butter contained the 

 Bacterium tuberculosis. According to researches by 

 Briscoe and MacNeal themselves, two of six samples of 

 butter contained tubercle bacilli virulent to guinea pigs. 

 Later Briscoe 2 reports the duration of life of the Bacterium 

 tuberculosis in butter, as found by other investigators, to 

 vary from four days to six months. His own work showed 

 tubercle organisms to be alive at the end of 274 days at 

 10 C. below zero, and 4 and 20 C. above zero. This 

 shows that the Bacterium tuberculosis is just as active 

 after the butter has been held in cold storage as when it 

 has been kept at higher temperatures. Mohler, Washburn, 

 and Rogers 3 state : " The work recorded in our investiga- 

 tions, as well as that by contemporaneous writers, proves 



1 Briscoe, Chas. F., and MacNeal, W. J., Tuberculosis of 

 Farm Animals, Univ. of 111. Agri. Exp. Sta., Bui. 149, 1911. 



2 Briscoe, Chas. F., Fate of Tubercle Bacilli Outside the 

 Animal Body, Univ. of 111. Agri. Exp. Sta., Bui. 161, 1912. 



3 Mohler, John R., Washburn, Henry J., and Rogers, Lore A., 

 The Viability of Tubercle Bacilli in Butter, U. S. Dept. Agri., 

 B. A. I., Ann. Rpt., pp. 179-191, 1909. 



