30 THE SPIRIT OF THE SOIL 



them by chloroform and other similar means, and it 

 seems as if the burning of cultivated soil by the 

 Indians, a practice dating back to traditional periods 

 of Indian agriculture, may have had as one of its 

 benefits the destruction of the protozoa of the soil.* 

 Fortunately they are less resistant than the bacteria, 

 and when these stringent methods are employed all 

 the protozoa perish, while a considerable number of 

 the bacteria are left, and these, rid of the protozoan 

 enemies, are able to jump into an amazingly rapid 

 development and continue their work of securing a 

 suitable soil environment for the plants. It is, 

 however, only in excessively manured soils that they 

 constitute a serious problem, and this short account 

 given of them may therefore suffice. 



* Cf. Virgil, Georgics : 



" Often you will find it well to burn 

 The garnered field and set the flimsy straw 

 A-cackling in the flames. Whether perchance 

 The land in this wise finds some unknown force, 

 Some fat enrichment ; or that every fault 

 Thereby is purified by fire, and all 

 The useless humours purged ; or that the heat 

 By its own virtue loosens secret pores 

 And paths unseen whereby the sap may flow 

 To the young grasses." 



