no Bulletin 65. 



Indestructibility of the Germ. 



Drying and heating — The substance of a tubercle, like expecto- 

 ration, may be dried up and reduced to powder without lowering 

 its virulence provided too much heat has not been emploj'^ed in 

 the drying. Although an absolute heat of 158° Fah. for 15 

 minutes is fatal to the germ yet in virulent masses, as in meat, 

 it is difl&cult to determine the actual temperature at all points and 

 tests are therefore often misleading. Thus Toussaint found that 

 broiled steak, the interior of which by his tests had reached 163° 

 to 176° Fah. was still infecting, Martin heated tuberculous mat- 

 ter in sealed tubes to 212° Fah. and found that even then some 

 germs would exceptionally escape. Chauvean and Arloing found 

 that nothing survived half an hour of the boiling temperature 

 and Galtier found that 162° Fah., which coagulates albumen, 

 sterilized completely if kept up for a sufficient length of time. 

 If in cooking meat, the blood (albumen) is not coagulated but 

 oozes out as a red fluid the temperature has not been enough to 

 ensure the death of the bacillus. Where there is a risk of tuber- 

 culosis therefore rare steaks must be refused. 



In milk as in meat heat is effective but at 162° Fah. the con- 

 tinued albumen is coagulated, the liquid acquires the boiled 

 flavor, a tendencj' to constipate, and a diminution of its digesti- 

 bility and nutritive qualities. In sterilizing this liquid, therefore, 

 for infants and invalids, it is better to keep the temperature at 

 158° Fah. for a longer period, say half to one hour continuously. 



Dr5nng of the tuberculous matter in doors or in the shade, and 

 apart from the above temperature, and its inhalation as fine dust 

 is one of the most common causes of tuberculosis. In one store 

 with a tuberculous clerk the dust raised in sweeping out the store 

 infected clerk after clerk, and a similar rising of the virus in dust 

 is a cause of infection in dwelling houses, stores, barns, barn- 

 yards, stockyards, and railroad cars. It is now allowed that the 

 infecting matter dried on the handkerchief, and shaken out on the 

 air is one of the most prolific sources of infection. So in animals, 

 a manger smeared with the discharge of a diseased animal, retains 

 the virus in an infecting state and infects the next susceptible 

 animal fed from it. Hence long before the days of Koch and his 

 discovery of the bacillus, the infection of animal after animal 

 which occupied the same stall in succession had convinced ob- 



