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 to a 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 



