202 PHYSIOLOGY OF BACTERIA 



This leads to another observation which belongs to 

 the same group of unexplained facts, and which has 

 become quite conspicuous perhaps only because it has 

 the interesting name '^bios theory" attached to it. 

 The bios theory dates back to the observation of Wildiers 

 (1901) that 0.25 c.c. of a yeast suspension transferred 

 to a synthetic medium would not develop while 2.5 

 c.c. transferred to the same medium would grow. This 

 is nothing else but an extreme case of lag with a very 

 small inoculum into a poor medium. 



These observations have since been repeated, con- 

 tested and verified, and explained in many different 

 ways. A literature review is given by Tanner (1925). 



The decrease of lag time by a larger inoculum would 

 speak in favor of the presence of small amounts of toxic 

 compounds in the new medium (assumption of Kruse 

 and Henneberg). The absence of lag in transferring 

 young cultures forbids this as a general explanation. 

 Where this explanation is correct, the lag period should be 

 greatly shortened by a good adsorbent like charcoal in 

 the medium. 



It is also imaginable that the resting cells store a 

 certain compound which allows the cells later to grow 

 at a more rapid rate, than if they depended upon food 

 from outside only. This would require a distinct cycle; 

 a stage of slow growth, with storage, followed by a stage 

 of rapid growth, partly at the expense of the stored food. 

 There is no evidence to support this assumption. 



One other explanation remains, namely, that by a 

 required oxidation — reduction potential. A number of 

 experiments are on record showing a better initial growth 

 if the dissolved oxygen is partly removed from the 

 medium. Perhaps the most typical example is the 

 observation of Webster (1925) that Bad. lepisepticum 



