62 SOIL AND SEWAGE 



in one case 26,000,000, and in the other 115,000,000 bacteria 

 per gramme. 



The number of spores relative to the total number of 

 bacteria in soil is large, the proportion being often as high 

 as from I to 10 to I to 3. 



The presence of organic matter undoubtedly has some 

 influence upon the number of bacteria in soil. 



Reimers 1 , examining graveyard soil, found an increased 

 number of bacteria in the vicinity of the coffin, the greatest 

 number being met with some distance above it. 



Young 2 examined bacteriologically 23 samples of soil all taken 

 from graveyards, some being from soil which had never been 

 disturbed, others being taken from the vicinity of old interments. 

 He found that the number of bacteria present in soil which 

 had been used for burial exceeded the number in undisturbed 

 soil at similar levels, and that this excess, though apparent at 

 all depths, was most marked in the lower reaches of the soil. 

 Roughly speaking, at the lower depths (8 9 feet) the soil 

 used for burials contained about twelve times as many bacteria 

 as the undisturbed soil and at moderate depths (4 6 feet) about 

 six times as many bacteria. 



The bacteriology of soil has been very incompletely worked 

 out, but in addition to the nitrifying bacteria, which are only 

 isolated by special methods, the saprophytic bacteria which are 

 commonly met with are Cladothrix dichotoma, B. proteus vtdgaris 

 and other proteus strains, B. subtilis, B. mycoides, B. megatherium, 

 B.fluorescens liquefaciens, B.fluorescens non-liquefaciens, B. arbores- 

 cens, and micrococci of different kinds. 



The bacteriological examination of soil from the public 

 health point of view is of but limited utility, its chief value 

 being in connection with the contamination of water from 

 surface washings. 



Pathogenic bacteria in soil. 



Pathogenic bacteria from various sources are constantly 

 gaining access to soil, and accurate knowledge as to their 



1 Zeitschr.f. Hygiene, 1889, vol. vii, p. 307. 



2 Trans. Royal Soc. of Edinburgh > 1895, vol. xxxvn, p. 759. 



