THE VITAL CONDITIONS OF BACTERIA. 85 



pie, bacterium typhi) or with difficulty (for example, 

 micrococcus gonorrhoese) in artificial nutrient media. 

 Among the inhabitants of the inanimate surroundings 

 of man, the so-called saprophytes, the majority can be 

 easily cultivated in the same artificial media as para- 

 sites; while in others, for example certain salivary 

 and water bacteria, such cultivation meets with in- 

 surmountable obstacles. 



All nutrient media must be rich in water, and the 

 presence of salts and of a supply of carbon and nitro- 

 gen is also indispensable. The majority of the prac- 

 tically important and all the pathological varieties 

 have a predilection for albuminous and feebly alka- 

 line nutrient media. 



The demands of the bacteria upon the composition 

 of the nutrient media vary extremely. As Mead Bol- 

 ton showed, a number of water bacteria (bacillus 

 aquatilis Fliigge and bacillus erythrosporus Fliigge) 

 are satisfied with water which has been distilled twice 

 in glass vessels. Here the proliferation of the bacte- 

 ria must have taken place either at the cost of traces 

 of impurities or of the ammonia and carbonic acid of 

 the atmosphere. 



In water which contained ammonium carbonate as 

 the sole source of carbon and nitrogen, and was ac- 

 cordingly free from all organic nutritive material, 

 Heraeus observed abundant proliferation of a variety 

 of fungus that is, a development of cell substance 

 from the simplest material, such as occurs otherwise 

 only in the higher plants which work with chlorophyll 

 in combination with sunlight. Hiippe and particu- 

 larly Winogradsky have shown the correctness and 

 importance of this observation as the result of care- 



