388 Proceedings of the Royal Physical Society. 



couple of loops, one near each end of the wire (Fig. 1, 

 Plate XVIII.). To these loops are tied the ends of short 

 silk threads, so that for the greater part of the length of the 

 wire there is a thread running parallel with it. Around the 

 rod near its upper end wrap a layer of cotton, so arranged 

 that when the rod is introduced into a J-inch test-tube the 

 wadding acts as a plug. The whole is then sterilised in the 

 hot-air chamher as above (Fig. 2, Plate XVIII.). 



Lastly, prepare a few dozen J-inch test-tubes by washing 

 them thoroughly, then filling them for a couple of inches with 

 distilled water ; plug these with cotton waddings and sterilise 

 them in the steam chamber. 



Everything is now ready. Suppose.it is wished to deter- 

 mine the action of a solution of some antiseptic on any 

 specific bacterium, say the Bacterium Termo. This may be 

 done, either by -leaving the antiseptic to continue its action, 

 or it may be allowed to act on the micro-organism for a short 

 time only. In the first case pour a small portion of the fluid 

 in which the B. Termo has been cultivated, into a shallow, 

 clean, sterilised dish, which may be covered with a flat plate. 

 Also pour a quantity of the antiseptic fluid to be used into 

 one of the; test-tubes previously sterilised, and replace the 

 plug. Now withdraw one of the wires from its test-tube, 

 and immerse the point with the attached silk thread in the 

 B. Termo solution. As the thread is quite dry, having been 

 heated in the dry chamber for so long, moisture (and with it 

 the bacteria) is drawn into the thread at once. This wire, with 

 its thread, is then introduced into the test-tube containing 

 the antiseptic fluid, the plug around the rod taking the place 

 of the plug that has been removed. The thread must be left in 

 this antiseptic fluid for some little time, as otherwise, having 

 been already moistened with the other fluid, it does not be- 

 come thoroughly impregnated. After being allowed to remain 

 in this, say for ten minutes, the thread is transferred to tlie 

 gelatine or other medium, either plunged straight into it, or 

 , by slightly bending the wire the greater part of the thread 

 is brought into contact with a sloping surface of agar-agar or 

 gelatine. In this case the supposed antiseptic is allowed to 

 remain, and it is soon seen whether, in the strength of solution 



