27 
THE TRUE POSITION OF THE TUBERCLE BACILLUS. 
Some of the more recent work upon the viability of the tubercle 
bacillus indicates that it has little if anv greater resistance to heat, 
dryness, putrefaction, chemicals, sunlight, and other injurious agen- 
cies than the great bulk of nonspore-bearing bacteria. Its usual 
habitat in albuminous, mucoid, or fatty substances, such as pus, muco- 
pus, necrotic material, milk, etc., protects it to a certain extent. This 
protection, however, is an accident of its environment rather than an 
inherent vital property. 
We now know that 60° C. for twenty minutes is sufficient to kill 
the tubercle bacillus in milk, bouillon, water, and other fluids.® At 
one time it was believed that the tubercle bacillus resisted boiling 
temperatures. Experiments have resulted in gradually reducing the 
accepted thermal death point, until now we can state with con- 
siderable confidence that the tubercle bacillus has very little more re- 
sistance than a number of other nonspore-bearing bacteria; for 
instance, the typhoid bacillus, the dysentery bacillus, and the colon 
bacillus. 
Some writers seem to consider it rather remarkable that the 
tubercle bacillus — an organism without a spore — should live several 
months in dust, in water, on fabrics, in sputum, etc. For instance, 
Schill and Fischer found it alive one hundred and eighty-six days in 
dried sputum; Toma virulent up to ten months; Sawizky dead after 
two and a half months; Twitchell found it virulent on a handkerchief 
seventy days but dead in one hundred and ten days ; Rickards, 
Slack, and Arms found it virulent after eighty-five days, kept dark 
and dry; and Feltz found dried sputum in a room virulent up to 
seven and nine months. 
It is possible, however, to cite from the literature instances of other 
nonspore-bearing organisms living similar periods of time under like 
conditions. For instance, observers have found that the cholera 
spirillum may live for one hundred and fifty to two hundred days 
when dried under favorable conditions. Sirena and Aiessi report 
that such a frail organism as the Diplococcus 'pneumoniae did not die 
until after one hundred and ninety-two days when dried on silk 
threads and kept in a moist r.oom, and one hundred and' sixty-four 
davs in a drv room. 
«> C/ 
In some experiments on the plague bacillus I found it to live over 
four months on a piece of dry sponge and over three months in water 
under laboratory conditions. 5 Similar instances might be multiplied. 
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, Washington, 
1808, pp. 85. 8°. 
b Rosenau, M. J.: Viability of the Bacillus pestis. Hyg. Lab. Bull. No. 4, U. S. 
Marine-Hospital Service, Washington, 1901. 
