1909.] The Electrical Reactions'of certain Bacteria, etc. 317 



It was important to decide the relationship of these bacterial movements to 

 the bacterial vitality. In point of fact the accumulation occurs in boiled, i.e. 

 dead, as well as in living cultures. As regards the probable nature of the 

 movement of the bacteria under the action of the current, we, are in the 

 presence of the following alternatives : — 



(1) If bacteria possess electric charges, they might be attracted to the 

 electrode of opposite sign, and migration of the bacilli would ensue. 



(2) Minute particles suspended in fluids, through which a current is sent, 

 are known to be directed to the electric terminals. During the course of this 

 work solutions have been found in which no movement of the bacilli was 

 effected by the current. It will be seen from some experiments to be 

 described, that the phenomena are hardly to be explained on the lines 

 indicated above. 



(3) When a current passes through an electrolyte, the usually accepted view 

 of the main processes therein involved is that there is a movement through 

 the solution of the ions of the solute in opposite directions towards the 

 electrodes. If we suppose that some chemical affinity exists between the 

 ions and the bacteria, there is at once the possibility of migration of the 

 bacteria towards the electrode ; the transmission of the bacteria to the anode 

 in one electrolyte, and the cathode in another {e.g., the tubercle bacillus 

 proceeds to the anode in sodium chloride, and to the cathode in ammonium 

 sulphate) can be attributed to a chemical affinity between them and the ions 

 <if the electrolyte. 



The migration of bacteria in electrolytes having been established, the next 

 step was to ascertain whether bacteria present in very small numbers in a 

 pathological liquid would be transmitted to either electrode in an electrolyte, 

 and thus concentrated in a small volume of liquid for further examination. 



With this object in view, the tubercle bacillus in urine was chosen because 

 of the convenience in recognising the organisms without there being any 

 necessity of undertaking cultivation work. The chief conditions required for 

 the purposes of these experiments are that the electrolyte (1) should conduct 

 electricity well, (2) should not be destructive of organic matter, (3) should 

 form a colourless fluid in aqueous solution, (4) should yield no metal or 

 metallic oxide as a result of electrolysis ; for such action has been found to 

 mask bacterial aggregation. 



The search for a suitable electrolyte for the tubercle bacillus proved a long 

 and laborious one. The general method of experimenting was practically 

 identical with that described in which the U-tubes were used. The tubercle 

 bacilli from glycerine agar cultures were ground in a mortar, made into an 

 emulsion with water and added to the electrolytes under test. Out of 



