THE VITAL CONDITIONS OF BACTERIA. 93 



per cent peptone solutions if we do not wish to use 

 one of the non-albuminous media described on page 

 86. At all events, the bacteria which are to be com- 

 pared must be treated in exactly the same way, and, 

 if the results are to be published, the various condi- 

 tions of the experiment must be described in detail. 

 Of bacteria which are free from spores not much is 

 known concerning their varying resistance according 

 to variety and nutrient medium, but a few statements 

 in this regard have been made concerning staphylo- 

 cocci (Esmarch: Z. H., V., 1889, p. 72). 



A combination of disinfectants increases their 

 action. In particular, the addition of acid (hydro- 

 chloric or tartaric acid) intensifies the effect of subli- 

 mate, and also of solutions of phenol and cresol. 

 Moreover, the effect is more certain upon a few than 

 upon many germs, and greater at a higher than at a 

 lower temperature. 



4. DEFICIENCY OF FOOD AND WATER. 



If bacteria which require nutritious substances in 

 order to thrive are placed in distilled water, they 

 usually die rapidly (within a few days) . In spring 

 water (even when sterilized) , the duration of life is 

 usually not more than eight to fourteen days, and 

 proliferation is rare. In a series of cases, however, 

 a much longer duration of life had been observed 

 (vide Loffler : " Das Wasser u. d. Mikroorg.," Fischer, 

 1896). The sensitiveness of bacteria to a deficiency 

 of water varies greatly. Upon drying nutrient media 

 growth soon ceases. On the other hand, the dura- 

 tion of life upon nutrient media (agar, gelatin, 



