174 BACTERIA 



the long periods during which bacteria can retain vitality in 

 soil. Farm soils have, as is well known, been contaminated 

 with anthrax in the late summer or autumn, and have re- 

 tained the infectious virus till the following spring, and it 

 has even then cropped up again in the hay of the next 

 season. In 1881 Miquel took some samples of soil at a 

 depth of ten inches, containing six and a half million bac- 

 teria per gram. After drying for two days at 30 C., the 

 dust was placed in hermetically sealed tubes, which were 

 put aside in a dark corner of the laboratory for sixteen 

 years. Upon re-examination it is reported that more than 

 three million germs per gram were still found, amongst 

 them the specific bacillus of tetanus. Whether or not there 

 is any fallacy in these actual figures, there is abundant evi- 

 dence in support of the fact that bacteria, non-pathogenic 

 and pathogenic, can and do retain their vitality, and some- 

 times even their virulence, for almost incredibly long 

 periods of time. 



It is now some years since Sir George Buchanan, for the 

 English Local Government Board, and Dr. Bowditch, for the 

 United States, formulated the view that there is an intimate 

 relationship between dampness of soil and the bacterial dis- 

 ease of Consumption (tuberculosis of the lungs). The mat- 

 ter was left at that time sub judice, but the conclusion has 

 been drawn, and surely a legitimate one, that the dampness 

 of the soil acted injuriously in one of two ways. It either 

 lowered the vitality of the tissues of the individual, and so 

 increased his susceptibility to the disease, or in some way 

 unknown favoured the life and virulence of the bacillus. 

 That is one fact. Secondly, Pettenkofer traced a definite 

 relationship between the rise and fall of the ground water 

 with pollution of the soil and enteric (typhoid) fever. 1 A 



1 The conditions requisite for an outbreak of enteric fever were, according 

 to Pettenkofer, (a) a rapid fall (after a rise) in the ground water, (l>) pollution 

 of the soil with animal impurities, (c) a certain earth temperature, and lastly 



