46 CONDITIONS OF BACTERIAL LIFE. 



rapidlj' fatal; for the mesophilic, ^ about 60° (Forster); 

 for the thermophilic, 75°. A temperature of 100° is not 

 withstood by any bacterium free of spores for more than 

 a few minutes. 



7. MECHANICAL AND ELECTRICAL 

 INFLUENCES. 



In the first edition, at this point I reported the astonishing state- 

 ments of Meltzer, according to whom short, feeble shaking would 

 operate favorably upon the growth of fluid cultures of bacteria, while 

 more prolonged and more vigorous shaking or long-continued very- 

 feeble shaking would operate very unfavorably (Meltzer, Zeit. f. 

 Biol. XXX, ij. 464). 



Otto Appel, who, at my request, restudied the whole question, ar- 

 rived at entirely different results. No shaking of longer or shorter 

 duration injured the bacterial growth, except where very severe agita^ 

 tiou and the addition of glass pearls caused direct mechanical lesions 

 of the bacteria. Slight shaking, such as cultures experience when 

 placed upon the foundations of strongly working steam-engines, was 

 without eiiect. (Further communications thereon are found in the 

 Archiv tiir Hygiene.) 



Most of the previously observed effects of the electric current are 

 easily explained as due to the action of heat and electrolysis. Thiele 

 and Wolf demonstrated by means of new investigations, which are not 

 open to objection, that neither the passage of a constant or interrupted 

 current through a culture of bacteria, if electrolysis be avoided, nor 

 the placing of a culture in an interrupted current induction coil, in- 

 jures the bacteria (C. B. xxv, 6.50); ?. c, also the previous literature, 

 which in part contains remarkable assertions. 



8. INFLUENCE OF LIGHT AND RONTGEN 

 RAYS. 



The cultures of all bacteria are restricted in their growth 

 by direct sunlight. If the action is more prolonged, they 

 are subsequently less able to grow luxuriantly in the dark, 

 and there results a generation of weakened organisms 

 shown, for example, by incomplete liquefaction, slight pro- 

 duction of pigment, lessened virulence, etc., which only 

 regain their original properties after repeated transplanta- 



' According to Sternberg the following die at 56°: Streptococcus 

 pyogenes, Bac. anthracis, Bact. mallei, and Vibrio cholerte (Auier 

 Jour. Med. Sciences, July, 1887, 146). 



