BACTERIA IN THE AIR I09 



when surrounded with dust. The question of their power 

 of resisting long drying is an unsettled point. The power of 

 surviving a drying process is, according to Germano, pos- 

 sessed by the streptococcus. This is not the case with 

 cholera or plague. Dr. Germano classifies bacteria, as a 

 result of his researches, into three groups: first, those like 

 plague, typhoid, and cholera, which cannot survive drying 

 for more than a few hours ; second, those like the bacilli of 

 diphtheria, and streptococci, which can withstand it for a 

 longer period ; thirdly, those Hke tubercle, which can very 

 readily resist drying for months and yet retain their virul- 

 ence. It will be obvious that from these data it is inferred 

 that Groups i and 2 are rarely conveyed by the air, whereas 

 Group 3 is frequently so conveyed. Miquel has recently 

 demonstrated that soil bacteria or their spores can remain 

 alive in hermetically sealed tubes for as long a time as 

 sixteen years. Even at the end of that period the soil 

 inoculated into a guinea-pig produced tetanus.^ 



The presence of pathogenic bacteria in the air is, of 

 course, a much rarer contamination than the ordinary sap- 

 rophytes. Tubercle has been not infrequently isolated from 

 dry dust in consumption hospitals, and in exit ventilating 

 shafts at Brompton the bacillus has been found. From 

 dried sputum it has, of course, been many times isolated, 

 even after months of desiccation. M. Lalesque failed to 

 isolate it from the dry soil surrounding some garden seats 

 in a locality frequented by phthisical patients. The writer 

 also failed to isolate it from the same soil. But a very large 

 mass of experimental evidence attests the fact that the air 

 in proximity to dried tubercular sputum or discharges may 

 contain the specific bacillus of the disease. Diphtheria in 

 the same way, but in a lesser degree, may be isolated from 

 the air, and from the nasal mucous membrane of nurses, 

 attendants, and patients in a ward set apart for the treat- 



^ Annates de Micrographie. 



