§ 1] EFFECT OF MOLAR AGENTS UPON GROWTH 371 



The results of Hoevath's experiments were these. Tubes 

 which were shaken for 24 hours were clear at the end of that 

 period, while similar tubes kept at rest had become muddy 

 with bacteria in the same time. If, now, the shaken tubes 

 were kept at rest during a day in a warm oven, they, too, 

 produced a rich growth of bacteria. When, however, the tubes 

 had been shaken for 48 hours they not only were found clear, 

 but they did not become cloudy upon subsequent warming 

 (I, p. 99). The shaking during the briefer period had thus 

 merely interfered with the normal growth processes, but the 

 more prolonged shaking had resulted in the death of the 

 bacteria. 



Subsequent attempts by other workers to reproduce these 

 results, by the use, however, of other methods, partially or 

 completely failed. Reinkb ('80), indeed, found that in water 

 agitated for 24 hours bacteria had ceased to grow, but had not 

 been killed; in so far a confirmation of Hokvath. Other 

 investigators, however (Bxjchnee, '80 ; Tdmas, '81 ; Leone, 

 '85 ; Schmidt, '91 ; Russell, '92 ; and others), have either 

 obtained no effect upon the growth of bacteria, or have found 

 it increased by motion. The results seemed hopelessly dis- 

 cordant. 



The more recent work of Meltzer ('94) has, however, 

 brought these conflicting observations under one general law, 

 and has thus offered an interpretation of the varied results. 

 He pointed out first that the diverse results of previous investi- 

 gators were due to the use of different species of bacteria and 

 of different kinds and degrees of shaking ; in a word, to dis- 

 similar methods. Meltzeb employed pure cultures of bacteria 

 of ascertained species, and counted the colonies by the well- 

 known bacteriological methods. Shaking was either violent, 

 being done in a machine somewhat like Hoevath's ; or slight, 

 being done by hand. The media used were neutral salt solu- 

 tions, Koch's bouillon, or pure water. The results showed 

 that a slight shaking is advantageous to the metabolism of 

 Bacterium ruber in water. Thus, while a culture containing 

 950 colonies, left quiet, was reduced after 8 days to 259 

 colonies; shaken, it had at the end of the same period 1366 

 colonies ; and shaken with glass drops rolling loose in the tube. 



