GROWTH AND DEVELOPMENT OF BACTERIA. 43 



in water, in faeces, in sewage, in dust, and, in fact, prac- 

 tically everywhere, of bacteria that under artificial culti- 

 vation show no evidence of life at a temperature lower 

 than 60° to 65° C, and will even grow at such high 

 temperatures as 70° and 7S° C, a state of affairs almost 

 paradoxical, inasmuch as such extremes of temperature 

 are sufficient for the coagulation of albumin, and, in con- 

 sequence, generally incompatible with life. Rabinowitsch^ 

 has likewise described a number of species of these 

 thennophilie bacteria, as they are called ; but states that 

 it was possible in her experiments to obtain evidence 

 of their growth at a lower temperature (34° to 44° C), 

 as well as at the higher temperature mentioiifid by pre- 

 ceding investigators. 



The most favorable temperature for the development 

 of pathogenic bacteria is that of the human body, viz., 

 37.5° C. There are a number of bacteria commonly 

 present in water, the so-called normal water bacteria, 

 that grow best at about 20° C. 



Under natural conditions it frequently occurs that 

 the development of one species or group of species of 

 bacteria is directly dependent upon the functional ac- 

 tivities of another totally distinct species, the growth of 

 one group resulting in conditions that are of vital im- 

 portance to the existence of the other. This interde- 

 pendence of species is known as symbiosis. It is observed, 

 for instance, in the course of putrefaction, where, 

 through exhaustion of free oxygen by the actively 

 germinating aerobic varieties, the conditions are sup- 

 plied that enable the anaerobic species to develop and 

 exercise their biological activities. Again, through the 



^ Eabinowitscli : Zeitschrift fiir Hygiene tt. Infectionskranklieiten, 

 Bd, XX, Heft 1, S, 154 tP 164. 



