762 DR JAMES BUCHANAN YOUNG ON THE 



In all, twenty-nine different samples of soil were examined. Of these, six were 

 examined by chemical methods only, five by bacteriological methods only, while the 

 remaining eighteen samples were examined both chemically and bacteriologically. The 

 results of these examinations are appended in tabular form. In these tables 



The mark — means " not examined." 

 The mark means " none found." 



Comparing the results obtained, we see that the number of micro-organisms present 

 in soil which has been used for burial exceeds that present in undisturbed soil at similar 

 levels, and that this excess, though apparent at all depths, is most marked in the lower 

 reaches of the soil. 



For example : — In sample I., virgin soil, at a depth of 4 feet 6 inches from the 

 surface, the number of bacteria present was 53,436 per gramme of soil, whereas at the 

 same depth in similar soil which had been used for burial eight years previously (sample 

 19), the number of organisms present was 363,411 per gramme. A more striking 

 example is that of a sample at the same depth, below which there had been a burial 

 3|- years previously at a depth of 6 feet 6 inches (sample 12), where the bacteria 

 numbered 722,751 per gramme. "The most important fact developed by Fraenkel's 

 researches," says Sternberg in his Manual of Bacteriology, p. 659, "is that in virgin soil 

 there is a dividing line at a depth of from three-quarters to one and a half metres, below 

 which very few bacteria are found, and that consequently the ground water-region is 

 free from micro-organisms, or nearly so, notwithstanding the immense numbers present 

 in the superficial layers." 



This great diminution in the number of organisms in the lower reaches of the soil is 

 fairly well seen on comparing the number of bacteria present in samples 1, 2, 3, and 4, 

 being virgin soil from Grange Cemetery. The manner in which the dividing line 

 disappears in the case of soils which have been used for purposes of burial is readily seen 

 by glancing over the tabulated results. Although, as formerly, the number of organisms 

 in the lower strata is small when compared with the numbers present near the surface, 

 the difference is by no means so striking. In considering these figures, however, it must 

 not be forgotten that in samples from the same level in similar soils the number of 

 bacteria may vary, even in soils which have been undisturbed. 



That the amount of organic matter present in the soil is an important factor in deter- 

 mining the number of bacteria found, one can hardly doubt. But so many conditions 

 must be taken into account, such as the depth from the surface, the amount of moisture, 

 as well as the nature and temperature of the soil, and probably many other conditions 

 which may affect these minute organisms in ways as yet quite unknown to the bacteriolo- 

 gist, that no definite conclusions can be drawn. 



" Miguel, in 1879, estimated the number of bacteria in one gramme of earth collected 

 in the park of Montsouri, Paris, at a depth of twenty centimetres, at 700,000 ; and in a 

 cultivated field, which had been manured, at 900,000 " [Manual of Bacteriology, Stern- 

 berg, p. 568]. 



