1890.] modify the Virulence of the Bacillus of Tubercle. 67 



bacillary virus, and Professor Koch, in his addi-ess to the Inter- 

 national Congress at Berlin this year, lends the weight of his great 

 authority to the same opinion ; but, in neither case, is any proof given 

 of the truth of this view.* 



It was in order to test the influence of light, air, and dry soils upon 

 the virulence of the bacillus of tubercle that the following series of 

 experiments were devised. 



It was decided to expose tuberculous sputum : 



(a) In a locality (Bowdon) where the soil was dry and sandy 

 (about 100 feet in thickness) and where very few cases of phthisis 

 were known to have originated. It was to be placed in full daylight 

 or sunlight, and exposed to abundant streams of fresh country air. 



(6) A portion of the same sputum would be exposed under similar 

 conditions, in the same place, with the exception that it would be put 

 into a darkened chamber. 



(c) A third portion would be taken to a small four- roomed tene- 

 ment in Manchester, on a clay soil, without cellarage and badly 

 ventilated, but it would be placed on the window ledge, with as much 

 light as could there be obtained. 



(cZ) A portion would be placed in the same cottage, but in a dark 

 corner of a sleeping room in which it was known that three deaths 

 from phthisis had occurred within the space of six or seven years. 



(e) Finally, a portion would be exposed to used air coming from 

 a ward in a Consumption Hospital, in Bowdon, in darkness. These 

 intentions were fully carried out. 



Two collections of sputum were obtained : 



A. From a woman dying of phthisis, collected on April 25. This 

 specimen contained comparatively few bacilli. 



B. Also from a woman in an advanced stage of phthisis, collected 

 on April 27. This sputum contained abundance of bacilli. 



Sputum (A) was not considered to be very suitable for the purpose 

 owing to the sparseness of bacilli ; but it was decided to use it by 

 way of control experiment ; owing to an accident, the portions exposed 

 under conditions (c) and (d) were lost. 



These collections of sputum were divided into portions and placed 

 in watch glasses marked A. 1, A. 2, A. 3, B. 1, . . . , B 10. Some 

 of these watch glasses were exposed without further arrangement, 

 >ut others, where there might be a possibility of infection, were 

 enclosed in cages, so arranged that air could reach them through a 



* [Since this was written, I have learnt that Savitzky has ascertained that 

 phthisical sputum, exposed " at the ordinary room temperature, and generally under 

 all common life conditions," retains its infectiousness not longer than 2J months, 

 and, other conditions being equal, a sputum dried in darkness loses its infectious 

 properties within the same period as a sputum exposed to light. ' Med. Chronicle,' 

 Nor. 1890, p. 117.] 



