THE VITAL CONDITION'S OF BACTERIA. 101 



case of aerobic varieties, that a slight movement of 

 the fluid is usually secured). Hence a theoretical in- 

 terest alone attaches to the fact that, according to 

 Meltzer's recent investigations, brief or feeble shak- 

 ing of bacteria cultures in vessels one-third full acts 

 favorably on the development of the bacteria, while 

 constant and vigorous shaking for a number of hours, 

 especially when balls, of glass are placed in the fluid, 

 scatters the bacteria into a fine dust and kills them. 

 The various bacteria act in different ways (Ztsclir. f. 

 Biolog., XXX., p. 454). 



Meltzer makes the very remarkable statement that 

 the feeble tremor which a steam engine running day 

 and night communicated to the floor of a brewery 

 was sufficient to kill, in four days, all the germs of 

 bacillus mycoides and subtilis kept in a bottle of 

 nutrient fluid. 



Concerning our scanty knowledge of the influence 

 of the electrical current upon bacteria, vide Frieden- 

 thal: C. B., Part L, XIX., 319. 



The majority of the effects of the electrical currents 

 hitherto observed are readily explained by the action 

 of heat and electrolysis. 



8. EFFECT OF LIGHT. 



The development of many bacteria, perhaps of the 

 majority, is impeded by the action of diffuse daylight 

 upon the cultures, and still more by the action of 

 direct sunlight. After a time the bacteria lose the 

 power of proliferating freely in the dark and we ob- 

 tain a generation of feeble organisms ; for example, 

 they liquefy imperfectly, form pigment imperfectly, 



