1909.] The Electrical Reactions of certain Bacteria, etc. 319 



In order to apply the observed aggregations of tubercle bacillus as 

 a method of their extraction from tuberculous urine, the experimental 

 arrangements were altered as follows : — 



The modified U-tube (fig. 3) was filled with a mixture of tuberculous 



urine, ethylamine, lactic and bromic acids, thoroughly shaken previously. 

 In the narrow limb of the vessel a platinum foil strip was submerged, and 

 served for the transmission of current through the main column of fluid. 

 The gases liberated at this foil escaped by the narrow limb, and were thus 

 prevented from traversing the bulk of the fluid. In the broad limb a glass 

 tube was submerged slightly and traversed by a platinum wire, which just 

 touched the fluid surface. The lower end of the glass tube formed a 

 bacterial trap by arranging the circuit so that the platinum wire was the 

 cathode. On passing a current the tubercle bacilli contained in the 

 tuberculous urine in the vessel are conveyed to the cathode as in the U-tube 

 experiments ; they eventually enter the fluid enveloped by the submerged 

 end of the tube, and remain close to the platinum wire. After sufficient 

 time the wire was carefully lifted out, the glass tube slightly lowered in the 

 vessel, the top of the tube closed by the wet or greased finger, and lifted 

 away to a glass slide, and examined for tubercle bacilli. The fluid contained 

 in the trap was 2 or 3 minims in' volume, and strongly alkaline at the end of 

 the process, the bulk of the mixture remaining acid. This alkaline fluid was 

 acidified with a 10-per-cent. solution of acetic acid on the slide previously 

 smeared with albumen fixative ; it was fixed by heat and stained by the 

 ordinary Z N carbol f uchsin method. Tubercle bacilli were found in small 

 numbers in the early attempts. 



The following experiment, in which the centrifuge and the electric current 

 were compared in the detection of tubercle bacilli placed in very small 

 numbers in a test fluid, is given in illustration of the power of the electrical 

 method : — 



\ 



Fig. 3. 



