we 
BACILLUS OF TUBERCULOSIS. 273 
replaced by pieces of stiff manila paper fastened to the 
tube with a rubber band. By keeping the tubes in- 
clined no undue amount of condensation of water can 
collect in the bottom, and the upper portion of the 
serum remains moist. The only precaution to be 
applied to prevent infection with moulds is to thor- 
oughly flame the joint between the tube and cap, as 
well as the plugged end, before opening the tube.’’ 
At the Saranac Laboratory beef blood-serum is used 
in ordinary test-tubes, which are sealed by rubber caps. 
The tubercles are crushed between sterile glass slides 
and rubbed gently upon the serum surface. The serum 
itself must not be too firm. It should just be solid 
enough to stand upright. The results thus obtained 
by Trudeau and Baldwin have been as good as those 
reported by Smith. In our experience all methods fre- 
quently fail with those unfamiliar with them, especially 
when, as shown by microscopical examination, the 
tubercular tissue used contains very few bacilli. 
Pathogenesis. The tubercle bacillus is pathogenic not 
only to man, but toa large number of animals, such as 
the monkey, pig, cow, etc. Guinea-pigs are extremely 
susceptible, and are much used for the detection of 
tubercle bacilli in suspected material. When inoculated 
with the minutest doses of the living bacilli they 
usually succumb to the disease. Infection is most 
rapidly produced by intraperitoneal injection. If a 
large dose is given death follows in from ten to 
twenty days. The omentum is found to be clumped 
together in sausage-like masses and converted into hard 
knots, which contain many bacilli. There is no serous 
fluid in the peritoneal cavity, but generally in both 
pleural sacs. The spleen is enlarged, and it, as well 
18 . 
