334 BULLETIN No. 161 [November, 



of time that they remained alive and by the severity of the disease 

 produced in the guinea pigs inoculated upon the same days from 

 each of ,these samples. This difference, however, was doubtless 

 due mainly to the difference in drying. 



3. Tubercle bacilli in the manure of a naturally infected cow 

 were dead within two weeks after exposure. More experimental re- 

 sults are necessary before trustworthy conclusions can be drawn. 



4. Danger of infecting farm animals from tuberculous ma- 

 nure is indicated. 



DURATION OF LIFE OF BOVINE BACILLI IN GARDEN SOIL 



PURPOSE Some investigators state that tubercle bacilli will 



OF TEST live in soil and in dead carcasses buried in the 



soil from two to three years. If this be true, ma- 

 nure from tuberculous cattle when put upon cultivated fields which 

 are later used to pasture stock may be a source of infection for farm 

 animals, especially hogs. For this and other reasons it was thought 

 advisable to test the length of time a pure culture of bovine tubercle 

 bacilli will live in garden soil. 



The culture of bovine tubercle bacilli was of the 

 CULTURE same strain as that used in the experiment forarti- 



fically infecting the cow manure. About four milli- 

 grams of pure culture were obtained from a four-weeks' growth on 

 the surface of two large tubes of glycerine agar. The organisms 

 were carefully removed from the glycerine agar and emulsified as 

 described under "Cultures and Emulsions," page 315. 



cAivymi c The sample of soil with which the tubercle bacilli 



SAMPLE . . 



OF SOIL emulsion was mixed was obtained from a garden 



plot that had been in cultivation only two years. 

 Previous to that time, this plot of ground had been in sod for at 

 least fifteen years. The part from which the soil sample was ob- 

 tained had been well manured with horse manure the first year it 

 was under cultivation. The second year no manure was added but 

 the ground was well stirred and made into a lettuce bed. A suf- 

 ficient amount of this soil was obtained to fill a J4 -inch mesh wire 

 basket having the dimensions of 4x5x6 inches. This required 

 1700 grams. This pulverized soil was placed in a large pan and 

 the emulsion of tubercle bacilli sprinkled over it. These were 

 thoroly mixed by being constantly stirred for some time. The 

 amount of emulsion was sufficient to make the soil quite wet and 

 sticky. 



