66 MILK AND THE PUBLIC HEALTH CHAP. 



Beck, Galtier, and Rabinowitsch, each independently re- 

 porting in 1900, all obtained results showing a high degree 

 of resistance for the tubercle bacillus. Galtier, for example, 

 found that 5 minutes at 70 C. or even 85 C. was not always 

 sufficient to kill tubercle bacilli in milk. 



Bang's later work in 1902 avoids some of the earlier 

 errors. He found that while heating to 60 C. for 15 minutes 

 did not prevent peritoneal infection from tubercle bacilli in 

 the milk, such heated milk failed to set up tuberculosis in fed 

 animals. Exposure for 1 to 15 minutes at 65 C. killed the 

 tubercle bacilli, and so did momentary exposure at 70, 75, 

 80, and 85 C. 



On the other hand, investigations made in America show 

 a much lower resistance to heat, and the results of their work, 

 which appears to have been very carefully done, are entitled 

 to careful consideration. The work of Theobald Smith, Russell 

 and Hastings, and of Rosenau, may be especially mentioned. 



Smith, 1 using a standard temperature of 60 C., and working 

 with tubercle bacilli suspended in distilled water, normal saline, 

 and broth, found that 15 minutes at that temperature was 

 sufficient to kill the bacilli. With milk his results were less 

 uniform. When the milk was heated in closed receptacles 

 so that a surface scum was not formed, the tubercle bacilli 

 were killed by 15 minutes' exposure to 60 C., and were, there- 

 fore, not more resistant in milk than in other fluids. When 

 the milk was exposed to the air so that a pellicle formed 

 on the surface, this protected the bacilli, and Smith found that 

 it might contain living tubercle bacilli even after 60 minutes' 

 exposure to 60 C. 



Eussell and Hastings, 2 following up this work of Smith's, 

 carried out some experiments under practical conditions with 

 tubercle bacillus infected milk heated in a pasteuriser (Pott's 

 pasteuriser). This was a pasteuriser of intermittent type, i.e. 

 one in which a definite quantity of milk is heated for a definite 

 time. The pasteuriser was rotated to effect uniform tempera- 

 ture exposure of the milk. Tubercle bacilli cultures of bovine 

 origin were added to the milk. All the experiments were 



1 Journ. Exper. Medicine, 1899, vol. iv. p. 219. 



2 University of Wisconsin Agric. Experiment Stn., 17th Annual Report, 

 1900, p. 147. 



