82 THE BACTERIA UNDER PHYSICAL AGENCIES. 



to test Horvath's assertions. Working with beer yeast (i.e. not 

 bacteria), he ascertained that this organism developed better when 

 the liquid (beer wort) was set in motion by stirrers. The pro- 

 bability of this favourable influence of movement being due to 

 aeration is, according to Hansen, inadmissible, this latter effect 

 having been but slight. 



A year later the question was taken up by J. REINKE (I.). 

 An objection raised by NAGELI (II.) led him to try the effects of 

 movements more nearly approximating in amplitude to molecular 

 movements than were those produced in Horvath's experiments. 

 To this end he made use of sound waves, the end of a metal rod, 

 caused to emit sound by friction, being immersed in a glass filled 

 with Cohn's nutrient solution containing bacteria, and thereby 

 transmitting the wave-motion to the liquid. The experiments 

 showed that a considerable restriction, 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, C. 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- 

 worked with Monilia Candida, Saccliaromyces mycoderma, and 

 Oidium al/ncans, 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, how- 

 ever, be remembered that the experimenters who obtained favour- 

 able 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 apparatus 

 he was enabled to subject the test samples to 180 reversed move- 

 ments of an amplitude of 1 5 J inches (40 c.m.) 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 

 invariably smaller than at the commencement of the experiment. 



