1 68 PHARMACEUTICAL BACTERIOLOGY 



consideration) and upon non-fertile or poor soil, is no longer considered 

 scientifically correct. The transfer of such soils frequently caused trouble 

 and the harm done through the simultaneous transfer of objectionable 

 soil fungi, bacterial diseases and noxious weeds, far exceeded any gain 

 which was derived from the desirable soil bacteria which were also present. 

 Bacterial soil inoculation should- be made by means of pure cultures or 

 mixtures of pure cultures, properly activated by means of special culture 

 methods and culture media. Bacterial soil inoculation is at present merely 

 in its initial stages but the results thus far obtained are indeed promising. 

 The results of recent experiments suggest the possibility that each species 

 or kind of plant has associated with it, via the root system, certain bacteria 

 which are beneficial and even essential to its growth and development. 

 The farmer of the near future will no doubt inoculate all seed, about to 

 be placed in the soil, with pure cultures of the predominating beneficent 

 bacteria belonging to the crop plant in question. 



Soil Colloids and Soil Fertility. — Within recent years the chemists 

 and physicists have made certain very interesting observations regarding 

 the behavior of matter in very finely divided state suspended or dissolved 

 in hquids or in semi-liquids. It has been known for a long time that the 

 socalled soluble salts (chemical combinations of basic elements with acids) 

 when in molecular solution will pass through dialyzable membranes (as 

 parchment, films of collodion, sausage casings, dried and fresh skins of 

 animals, etc.), whereas certain other substances apparently also in solution 

 (usually organic in nature), will not pass through such membranes. All 

 substances apparently in solution but which will not pass through dialyz- 

 able membranes are called colloids. Recent investigations have shown 

 that all substances, organic as well as inorganic, may be changed or con- 

 verted into colloids. In other words, colloidality is a universal property 

 of matter. Thus, we have colloidal iron, colloidal gold, copper, silver, 

 mercury, etc., etc. The Hindoos have for many centuries, prepared and 

 used colloidal iron in the treatment of certain diseases, as anemia, and 

 other disorders in which iron compounds appear to be deficient. There 

 is already a vast literature deahng with the colloids of the soDs in their 

 relationship to the activities of soil bacteria and to soil fertiUty. To 

 review, or even to cite the most important contribution to these subjects 

 would be wholly impracticable in this introduction. It is indeed regret- 

 table that those who treat of and discuss the practical phases of cultural 

 operations and the use of soil fertilizers, do not explain, or at least briefly 

 indicate, the coUoidal principles involved. 



We may therefore, define colloids as very minute particles composed 

 of groups of molecules, dispersed in or held in suspension in various media, 

 hcus as water and other liquids, gases, and even in soUdsL It is generally 



