The Preservation of Health 



289 



449. Disease-Producing Bacteria in the Soil. Surface 

 soils, especially those rich in organic matter, abound in 

 many kinds of bacteria. There seems to be an intimate 

 relation between the soil and important bacterial diseases. 



The terrible disease called tetanus, or " lockjaw," is known 

 to be due to a micro-organism common in the soil of certain 

 localities. 



Typhoid bacilli were kept alive for 456 days by one 

 experimenter in soil which had been polluted with organic 

 matter. Farm soils have been contaminated with the 

 bacilli of anthrax, or malignant pustule (Fig. 157), and have 

 retained the infectious virus for several months. 



In brief, the disease-producing bacteria found in the 

 surface soils can and do retain their vitality, and some- 

 times even their virulence, for long periods of time. 



450. Disease - Pro- 

 ducing Bacteria in 

 Foods. Good food as 

 well as bad frequently 

 contains large num- 

 bers of bacteria. It 

 is fortunate, however, 

 that harmful micro- 

 organisms are usually 

 killed by cooking. 

 Not all the persons 

 eating infected food 

 suffer equally, and 

 oftentimes some 

 escape altogether. 



Bacteria have a 

 special fondness for milk. In a hundred different ways, milk 

 runs the risk of being polluted, as from the animal, the 



FIG. 1 58. Bacilli of Typhoid Fever. 

 (Magnified 1000 diameters.) 



