094 DISTRIBUTION AND HABITAT OF THE BACTERIA. 



substrata much less commonly; such are, for example, 

 the bac. mycoides (p. 403), and some other forms which 

 have not as yet been more minutely described. Various 

 kinds of bacilli must also be very often present in the 

 soil in the form of resting spores, as can be concluded 

 with certainty from disinfection experiments. 



Pathogenic Pathogenic forms are also not uncommonly found. 



bacteria te Well . known inhabitants of the soil are the bacilli of 

 malignant oedema, of infective tetanus, the bac. septicus 

 agrigenus, &c., which are commonly and almost ex- 

 clusively found in garden or field earth. Pathogenic 

 bacteria occur with such frequency in the soil that no 

 material found in nature so easily produces infection as 

 earth. If mice, guinea-pigs, or rabbits are inoculated 

 with a quantity (not too small) of earth from the surface 

 of the ground a much higher percentage of cases of 

 disease is obtained than when the inoculation is made 

 with some fluid containing bacteria. If large quantities 

 of the latter are injected a large number, or it may be 

 all of the animals die of ptomaine poisoning ; but an 



Frequency of infective disease only results in rare cases. We have 



action of the also reason to assume that the infective diseases caused 

 by the soil would be more numerous, and would lead to 

 the isolation of other species of pathogenic fungi, were 

 it not that these oedema and tetanus bacilli are so widely 

 distributed that they obscure the other infective agents 

 and cause the death of the animal before other moro 

 slowly growing bacteria have had time to multiply. 

 This marked infective property of the soil must evidently 

 make us a priori inclined to accept the view that the 

 soil is of special importance in the occurrence of human 

 infective diseases. 



Vital powers We have also obtained some information as to certain 



of theS eria effects produced by the bacteria on thesoil. Thus Schlosing 

 and Miintz, and at a later period Warington, showed that 

 the formation of nitric acid from the ammonia of organic 

 substances is chiefly caused by lowly organisms ; when 

 soil has been heated or treated with disinfecting means 

 it loses almost entirely this power, which is otherwise 

 constantly observed. In like manner Wollny and Fodor 



