196 



PHYSIOLOGY OF BACTERIA 



the age of the mother culture. He summarized his 

 experiments in the table reproduced in Table 49 and 

 drew from it the following conclusion: 



''The previous discussions show that besides the 

 well-known requirements (composition and reaction of 

 medium, optimal temperature, etc.), a new, heretofore 

 not considered factor is of importance for fastest possible 

 growth, namely inoculation from a very young culture, 

 not more than a few hours old." 



Table 49. — Initial Rate of Growth, and the Age of the Corre- 

 sponding Mother Cultures of Bact. typhosum 



Kruse (1910) believed the lag to be a case of poisoning by traces of 

 copper or other toxic substances adsorbed on the surface of the 

 bacteria after transfer. Henneberg (1926) suggested that substances 

 causing surface tension depression might be to blame for it. Though 

 neither of the two investigators gives any proof, these explanations 

 may hold true occasionally. But the phenomenon is too general 

 to be accounted for altogether in this way. 



The above explanation of Miiller (1895), accepted by 

 Barber (1908) and Penfold and Ledingham (1914), is 

 now generally assumed to be the best explanation of the 

 lag period. The transferred bacteria continue to multi- 

 ply for some time at the rate with which they multiplied 



