OF Trr.ickcu-: I>. UMLLI OTTSIDE THE ANIMAL BODY 335 



PLACE OF K rams ()1 lms infected soil were removed to 



EXPOSURE l)c tested for tubcrclo bacilli as a control. The re- 



maining soil was put into the wire basket and 

 covered with a wire gauze. It was buried in another garden that 

 had been under cultivation for one year and had received no ma- 

 nure or fertilizer of any kind. The place where it was buried had 

 been previously well pulverized. The basket with the infected soil 

 was buried six inches under the surface of the ground. 



TESTS OF Samples of this infected soil were tested for tuber- 



SAMPLES cle bacilli on the first day of exposure and on the 



7th, 1 6th, 34th, 55th, and thereafter about once 

 a month for 352 days. Ten grams of soil were removed by dig- 

 ging down beside the mouth of the basket and with a sterile pota- 

 to knife making an opening to the center of the basket. After the 

 removal of the sample, the opening was filled by pressing the soil 

 in around this opening with a potato knife. The wire gauze was 

 placed over the mouth of the basket and the garden earth filled in 

 over it to a depth of six inches. The soil sample taken to the lab- 

 oratory was thoroly shaken with 200 cc. of 0.8 percent salt solu- 

 tion in a 300 cc. flask. After standing ten minutes until the coarser 

 sediment had fallen to the bottom, 40 cc. were removed and placed in 

 two sterile centrifuge tubes and centrifuged for five minutes. The 

 supernatant liquid was drawn off and put into two other centrifuge 

 tubes and centrifuged for thirty minutes at 2000 revolutions per 

 minute. The supernatant liquid was drawn off and discarded. The 

 last 5 cc. of the liquor and sediment were thoroly mixed and in- 

 jected subcutaneously into guinea pigs, in graded doses, giving one 

 i l /2 cc., another i cc., and for the first test a third received Y 2 cc. 



RESULTS OF resu ^ s considering the length of time that 



THE TEST tubercle bacilli live in the soil are recorded in 



Table 20. The guinea pigs inoculated from 

 samples taken on the day of exposure, and on the 7th, i6th and 

 34th day after exposure showed in each case, when killed and ex- 

 amined, severe generalized tuberculosis. Microscopical and cul- 

 tural tests showed the germs from the diseased tissues to be char- 

 acteristic of active, living tubercle bacilli. Tests after this time indi- 

 cated a weakening in virulence, but slight tuberculosis was produced 

 in the test animals from material taken on the 21 3th day of expos- 

 ure. IV^croscopic, cultural, and guinea-pig tests from the diseased tis- 

 sues of the original guinea pig showed the tubercle bacilli in the soil 

 sample to be active and virulent. Five tests were made after this 

 date. In every case the guinea pigs, when killed and examined, 

 were found to be healthy. The two testings after the last one 

 in which tubercle bacilli were found, viz., the ones made on the 



