DISTRIBUTION AND HABITAT OF THE BACTERIA. 703 



bacteria as to lead to their destruction does not readily 

 occur in the soil, not even in the so-called dry soil, 

 because the air in it is saturated with moisture, and a 

 layer of vapour surrounds the elements of the soil ; but 

 that, on the contrary, as Soyka has suggested, the 

 arrangement of the fluid in the soil in thin capillary 

 layers surrounding the particles produces a sort of fixation 

 of the bacteria, and hinders such free circulation of the 

 organisms as occurs in thicker layers of fluid, and thus 

 both their overgrowth by other bacteria and their destruc- 

 tion by drying are avoided; and these two factors, which 

 are present in the soil in a very exceptional manner, lead 

 to preservation of non-spore-bearing pathogenic bacteria 

 to an extent which occurs much more rarely in other 

 substrata. 



The result that the soil may possibly be a particularly good Explanation 

 preserving medium for bacteria, but does not permit their of the marked 

 multiplication, seems opposed to the experience mentioned the^oih 1 ^ 

 above that a soil impregnated with putrid fluids sets up 

 infective diseases in animals much more readily than the 

 putrid fluids themselves. But this fact is easily explained 

 without assuming a multiplication of these bacteria. In 

 putrid fluids parasitic bacteria are present in very much 

 smaller numbers than the saprophytic forms, among which 

 some are always present which furnish very poisonous 

 ptomaines. On account of these ptomaines we cannot 

 employ large doses of the putrid fluid if we wish to obtain 

 an infection ; after the injection of large quantities the 

 animals only die of intoxication, and when on the other hand 

 small doses are injected the chances of an infection are very 

 slight on account of the relatively small number of the patho- 

 genic bacteria. If now the putrid fluids reach a porous soil 

 the individual bacteria are fixed and preserved, while there is 

 rapid destruction of the ptomaines. Numerous experiments 

 formerly performed, and also those carried on of late by Falk 

 and Soyka, have shown that the soil by its capillary attraction 

 splits up poisonous organic bases, and also ptomaines, in a 

 very short time. Hence we can introduce subcutaneously 

 into animals large quantities of an impure soil without in any 

 case causing intoxication, and hence with such a soil infective 

 diseases are much more easily produced than with the fluids 

 themselves. Very small quantities of the soil are usually 

 without any effect. 



The question now arises whether this supposed, but 



