1894.] Influence of certain Agents on the Tubercle-Bacillus. 55 



3. Papers were exposed to air and light for three days, February 

 20, 21, and 22. The rate of air current was about 1,000 ft. per hour, 

 and the sunshine recorded was one hour. Others were exposed for a 

 longer period. 



The amount of tuberculous dust was so small that portions of the 

 paper were inserted together with it, under the skin. 



Table IV. 



No. 

 151. 



191. 

 192. 



160. 

 170. 



First Set of Experiments. 



1. Sputum kept only one day in a closed, dark cupboard, after drying 



on paper, produced well-marked tuberculosis in 31 days. 



2. Sputum kept under the same conditions, but exposed to a little air for 



35 days, produced distinct local tuberculosis in 23 days. 



3. Idem. 



Second Set of Experiments. 



1. Sputum kept in the draught closet for three days in a current of air 



(about 1,000 cubic feet per hour) in darkness, at the ordinary tem- 

 perature, gave well-marked tuberculosis in 32 days. 



2. Sputum under exactly the same conditions gave well-marked tubercu- 



losis in 24 days. 



Third Set of Experiments. 



156. 1. Sputum exposed to light for three days, during which there was one hour 



of sunshine. Ventilation good. Temperature, maximum 50 and 

 minimum 38 F. No tuberculosis after 46 days. 



157. 2. Sputum under the same conditions as the last, except that it had 



not been- reduced to dust, gave the same negative results after 50 

 days. 



189. 3. Sputum exposed to light for seven days ; 15 hours of sunshine ; brisk 



ventilation. Temperature, maximum 88, minimum 29 F. No 

 tuberculosis after 22 days. 



190. 4. Sputum exposed to light for two days (after being kept dry for four 



weeks) ; short exposure to sunshine (not many hours) ; ventilation 

 slight. Temperature, maximum 60, minimum 22. No tuberculosis 

 after 22 days. 



It will be noted that in all the specimens exposed in the dark, 

 tuberculosis was the result, but it must be observed, that in the case 

 of those exposed in the draught-closet, only three days were allowed 

 to pass before they were removed from the influence of the air- 

 current. On the other hand, all the specimens exposed to both air and 

 light, whether for two, three, or seven days, were found to have en- 

 tirely lost their power for evil. 



The specimen exposed for two days only, had, however, been kept 

 for four weeks before being exposed to these influences, and it 

 had thus lost a portion of its virulence. 



These researches have an important bearing upon the question of 

 the limits of the infectiveness of tubercle. 



