60 BACTERIOLOGY 



teria are not so effected, a few species retaining their power 

 to germinate after having been dried, as the word is ordinarily 

 understood, for a comparatively long time, and spores have 

 been kept in a dry state for years without losing their power 

 to germinate. 



Influence of Electricity. The methods employed for 

 deciding this point have led to results that are inconclusive 

 and not easy of interpretation. 



It is true that when bacteria are exposed to the electric 

 current they are often inhibited and sometimes killed. 



This result may be interpreted in several ways, viz. : The 

 elevation of temperature caused by the current may explain 

 the destruction; the electrolytic action of the current on 

 matters in which the bacteria are located may, by dissocia- 

 tion, liberate agents that are destructive to bacteria, or a 

 similar destructive dissociation within the bacteria them- 

 selves may result from the action of the current. 



The evidence at hand does not permit of the acceptance 

 of either of these suggestions as the correct interpretation of 

 the results. 



Chemotaxis. Another interesting biological peculiarity of 

 bacteria is that discovered by Engelmann and by Pfeffer, 

 known as chemotaxis. This term applies to the peculiar 

 phenomena of attraction and of repulsion that are exhibited 

 by motile bacteria when in the presence of solutions of bodies 

 of various chemical composition. It was demonstrated 

 that the bacteria in decomposing infusions accumulate in 

 great numbers in the neighborhood of the sources of oxygen. 

 In a hanging-drop of such an infusion the bacteria will be 

 seen to a'ccumulate in a dense mass along the margin or 

 around the edge of small bubbles of air in the fluid. Even 



