29 
out the substance of the liver, spleen, lungs, etc., these secondary 
inoculations may not be necessary. 
The various organs (whether they contain macroscopic lesions or 
not), bits of tissue, and parts of lesions should be ground up with 
salt solution and the extract injected into the peritoneal cavity of 
a normal (“ secondary ” ) guinea pig; if the bacteria are alive there 
will develop a generalized fatal tuberculosis; if dead, only a trifling 
slight localized process. This method is time consuming and expen- 
sive, but is often indispensable as a final test. 
It is well known that tuberculin can not distinguish the lesions 
produced by live tubercle bacilli from those produced by dead ones. 
In a series of experiments on this point I found that three out of 
eight guinea pigs with lesions produced by dead tubercle bacilli 
died as the result of a subcutaneous injection of 2 c. c. of tuberculin 
(O. T.).° 
AN EXPLANATION OF DISCREPANCIES IN PUBLISHED REPORTS. 
When one reads the literature upon the subject of the viability 
of the tubercle bacillus he is struck first by the extravagant claims 
made by some investigators for the prolonged life and unusual resist- 
ance of the tubercle bacillus. There are also marked discrepancies 
in the results obtained by different experimenters with apparently 
well-planned and carefully controlled work. 
It seems that one of the main reasons for these variations is the 
failure to take note of the pathogenic power of the dead tubercle 
bacillus. In 1884 Scliill and Fischer studied the action of a tempera- 
ture of 100° C. upon tuberculous sputum. They reported that 100° 
C. of dry heat did not surely destroy the virulence of tuberculous 
sputum, whether dry or moist. These experiments are frequently 
quoted to show that the tubercle bacillus resists boiling temperatures; 
but we now know that the thermal death point of the tubercle bacil- 
lus is considerably less than that indicated bv earlier work. 
Scliill and Fischer also found that the bacillus retained life in 
sputum dried one hundred and forty-three days, but was not infect- 
ive after one hundred and seventy-nine days. The method used 
consisted in inoculating guinea pigs, but the authors do not give the 
details of the experiments. 
In view of the fact that earlier investigators fell into error concern- 
ing the thermal death point of the tubercle bacillus, it may be assumed 
that a repetition of their work upon the viability of the organism 
when dried in sputum, etc., may cause us to revise our views upon 
the subject. 
a Rosenau, M. J.: The thermal death points of pathogenic microorganisms in milk. 
Hyg. Lab. Bull. No. 42, U. S. Public Health and Marine-Hospital Service, Washing- 
ton, 1908, pp. 85. 8°. 
