38 
De Man states that few, if any, of these authors recite the condi- 
tions and methods of their experiments. He used material from the 
substance scraped from the cut surface of tuberculous udders, and 
in some instances tubercular sputum. The work was done in the 
same manner as Forster’s, q. y., and is apparently a part of or a 
continuation of the same series of experiments. His results may be 
condensed as follows: 
Tubercle bacilli are killed by the following temperatures: In udder 
juice, 55° after four hours exposirre, 60° after one hour exposure (not 
after forty-fiTe minutes), 80° after fiye minutes exposure, 90° after 
two minutes exposure, 95° after one minute exposure; in sputum, 
65° after fifteen minutes exposure, 70° after ten minutes exposure. 
Exposure for less time failed to kill. Control animals injected ^yith 
unheated material became tubercular. 
Smith,® 1899, says, in criticism of this work, that such dense 
suspensions can not be used to determine the thermal death point to 
be compared yfith those of other bacilh, nor can they be regarded as 
imitating the conditions under which tubercle bacilli occur in milk. 
It might be added that De Man’s work at two yery interesting tem- 
peratures (65° and 70°) was performed with sputum and not eyen 
udder juice. 
Schroeder,^ 1894, obtained what may be regarded as an early hint 
that comparatiyely low temperatures may be effectiye in killing the 
tubercle bacillus in milk. TTith most other observers at that time, 
he had been led to regard the tubercle bacillus as a nonspore-bearing 
pathogen almost unique among this class in its resistance to heat. 
He acted upon the adyice of Yersin who, at the suggestion of Roux, 
attempted to make use of this property to rid milk of those other 
organisms which frequently produce disease or death when injected 
into animals. Schroeder, attempting to discoyer the presence of 
tubercle bacilli in market milk, heated the specimens to 60° for 
fifteen minutes before injection. Fortunately, he controlled tins 
procedm’e ^yith milk artificial^ inoculated vfith tubercle bacilli, and 
the faihne to get tuberculosis in market milk specimens was paral- 
leled with, a similar failure in the controls. The inference was that 
60° for fifteen nnnutes could, under some circumstances, kill tubercle 
bacilli. 
TFoodhead,'' 1895, obtained yery discordant results, which it is 
difficult to interpret. It is probable that they are explained, in the 
« Smitli, Theobald : The thermal death point of tubercle bacilli in milk and other 
fluids. Joum. Exper. Med., vol. 4, 1899, p. 217. 
& Schroeder, E. C.; Further experimental observations on the presence of tubercle 
bacilli in the milk of covs. E. S. Bur. An. Industry, Bull. 7, 1894, p. 75. 
c Woodhead, G. Sims: Keport of the Koyal Commission appointed to inquire into 
the effect of food derived from tuberculous animals on human health. Parts 8, 9, 12, 
and 13. 1895. 
