64 THE BACTERIA UNDER PHYSICAL AGENCIES 



with Cohn's nutrient solution containing bacteria, and thereby transmitting the 

 wave-motion to the liquid. The experiments showed that a considerable restric- 

 tion, but not cessation, of growth occurred. From this Reinke concluded that " if 

 it be assumed that the molecules of living protoplasm are endowed with specific 

 vibratory movements, the idea appears feasible that when those specific molecular 

 vibrations are crossed by other molecular motions of external origin, the vital 

 functions of the protoplasm will be weakened." 



The labours subsequently made public by L. Tumas, 0. Roser, H. Buchner, 

 H. Cramer, H. Miquel, H. Leone, A. Gartner, B. Schmidt, and others, did not 

 produce anything having a material bearing on this question. A treatise by 

 H. RUSSELL (I.), who workediwith Monilia Candida, Saccharomyces mycoderma, and 

 Oidium albicans, and found that the form and dimensions of the cells are but 

 little altered by agitation, and that the percentage of germs in agitated samples 

 is almost double that in samples left at rest for the purpose of comparison, is, 

 however, worthy of mention. 



The results appear to contradict one another. It should, however, be re- 

 membered that the experimenters who obtained favourable results with agitation 

 subjected their cultures to comparatively gentle movements, whereas the motion 

 set up by Horvath was violent and prolonged. The conditions of his experiment 

 were first repeated by S. MELTZER (I.) in 1891, who worked chiefly with Bacillus 

 megatherium. He made numerous experiments, but we will only draw attention 

 to those that gave results in advance of those previously obtained. A New York 

 mineral water works placed at Meltzer's disposal their agitator, with which appa- 

 ratus he was enabled to subject the test samples to 180 reversed movements 

 of an amplitude of 15^ inches (40 cm.) per minute. The flasks employed were 

 only one-third full. Meltzer found that the number of germs (ascertained by the 

 plate method) in the agitated example in no instance amounted to as much as 

 one-tenth of those in the unshaken check samples ; and was, in fact, almost in- 

 variably smaller than at the commencement of the experiment. The restriction 

 of reproduction thus indicated increased with the duration of the treatment, so 

 that by this means the liquid could be completely freed from germs. The effect 

 was even more powerful when sterilised glass beads were added before commenc- 

 ing the operation, the complete annihilation of the germs being accomplished 

 under these conditions by ten hours' agitation. In addition to B. megatherium, 

 Meltzer also included a micrococcus (presumably M. radiatus, Fliigge) and a 

 short motile bacillus (albus ? ) in the scope of his investigations. A difference in 

 the degree of resistance to this kind of inhibition is inherent in these organisms, 

 since it was found possible to successively eliminate each form from a mixture of 

 the three species. B. megatherium, as the most susceptible, disappeared first, and 

 was followed, in order, by Micrococcus radiatus and Bacillus albus. The cells were, 

 as a result of the shaking, split up, not into visible debris, but into an indistin- 

 guishable fine powder, a circumstance showing that the destruction of the vitality 

 of the cell was not the result of a coarse mechanical disruption, but was due to a 

 much more refined process; as was, in fact, shown by the further researches 

 made by the same observer. He left several flasks containing cultures of B. mega- 

 therium or B. subtilis in solutions of common salt, to stand for several days in the 

 engine-house of a large New York brewery, wherein, in consequence of the unin- 

 terrupted working of the engine, an incessant vibration was produced throughout 

 the room. After four days all the germs in the several flasks were dead, whilst 

 energetic reproduction had proceeded in the check samples placed in a quiet spot. 

 Consequently, not only violent shocks, but also minute vibrations, exhibit the 

 power of retarding the growth of bacteria, and even killing the organism. 



Motion may, however, also exert a favourable influence, and especially when it 

 is comparatively weak, reproduction being thereby accelerated, as has been moie 



