64 SOIL AND SEWAGE 



diphtheria bacilli may remain alive for 18 days in moist warm 

 modelling clay. 



B. pestts. The Advisory Committee on Plague in India 

 report 1 some experiments on this bacillus in soil. They studied 

 how long floors grossly contaminated with plague bacilli would 

 remain infective for animals, the infectivity being tested by 

 rubbing scrapings into susceptible animals. They found that 

 cow-dung floors remained infective for 48 hours, while floors 

 composed of a mixture of sand and lime allowed to set did 

 not remain infective for over 24 hours. 



Gladin claims to have recovered the plague bacillus after 

 two months from unsterilised earth, but Mackie and Winter 

 (quoted in the above report) found the bacillus (with difficulty) 

 up to 96 hours after its introduction, but not subsequently 

 either by culture or animal inoculation. 



It would appear that, in general, B. pestis dies out rapidly 

 from soil. 



B. antJiracis. As is well known, spores of the anthrax 

 bacillus may live and retain for years their virulence in soil 

 to which they have gained access, and such infected land if 

 used for grazing purposes may serve as a means of infection 

 for very prolonged periods. 



A number of anaerobic, pathogenic bacteria are common soil 

 organisms. In particular the bacilli of tetanus and malignant 

 oedema are widely distributed in soil, especially when cultivated. 

 For their characters and general methods of isolation, general 

 text-books on Bacteriology should be consulted. 



Excretal bacilli in soil. 



The presence and viability of the common excretal bacilli 

 in soil is a matter of considerable public health importance, 

 particularly in relation to water supplies. Soils which have 

 been recently contaminated with organic matter in quantity 

 for example, by sewage or manure show evidence of this when 

 bacteriologically examined. 



Houston 2 , in a prolonged series of experiments, watered 



1 Journ. of Hygiene, 1906, vol. VI, No. 4 (extra No.). P- 509. 



2 Local Govt. Board Med. Officer's Report, 1900-1, p. 405, and 1901-2, p. 355. 



