686 
The above tabular statement shows that my results agree with the 
work of Yersin. Bonhoff, Schroecler. Th. Smith, Bussell and Hast- 
ings. and Hesse in that 60° for twenty minutes is sufficient to kill the 
tubercle bacillus. 
The lesions produced by a large mass of dead tubercle bacilli may 
be distinguished by their extent rather than by their character. In 
doubtful cases secondary inoculation is the only trustworthy method 
of determinmg whether the bacilli are alive or dead. The tuberculin 
test does not differentiate between the live and dead tubercles. Three 
guinea pigs out of eight having lesions produced by dead tubercle 
bacilli (killed at 100° C.) died as the result of the subcutaneous inoc- 
ulation of 2 c. c. tuberculin (O. T.). 
CONCLUSIONS. 
The evidence is plain that milk heated to 60° C. and maintained at 
that temperature for two minutes will kill the typhoid bacillus. The 
great majority of these organisms are killed by the time the tempera- 
ture reaches 59° C., and few survive to 60° C. 
The diphtheria bacillus succumbs at comparatively low tempera- 
tures. Oftentimes it fails to grow after heating to 55° C. Some 
occasionally survive until the milk reaches 60° C. 
The chokra vibrio is similar to the diphtheria bacillus so far as its 
thermal death point is concerned. It is usually destroyed when the 
milk reaches 55° C. ; only once did it survive to 60° C. under the 
conditions of the experiments. 
The dysentery bacillus is somewhat more resistant to heat than the 
typhoid bacillus. It sometimes withstands heating at 60° C. for five 
minutes. All are killed at 60° C. for ten minutes. However, the 
great majority of these micro-organisms are killed by the time the 
milk reaches 60° C. 
So far as can be judged from the meager evidence at hand, 60° C. 
for twenty minutes is more than sufficient to destroy the infective 
principle of Malta feA'er in milk. The J/. melitensis is not destroyed 
at 55° C. for a short time; the great majority of these organisms die 
at 58°, and at 60° all are killed. 
Milk heated at 60° C. and maintained at that temperature for 
twenty minutes may therefore be considered safe so far as conveying 
infection with the micro-organisms tested is concerned. 
