Simple Method of Testing the Efficacy of Antiseptics. 387 



In setting about this, it was necessary to bear in mind the 

 following points : 



{a) An antiseptic may act in one of many ways — a very 

 minute portion of an antiseptic may prevent the growth and 

 development of a micro-organism in a nutrient medium, but 

 the micro-organism may, when removed from the presence 

 and restraining action of the antiseptic, again begin to flourish 

 and grow. A stronger antiseptic may kill the micro-organism 

 outright, and so on. One must therefore find a method by 

 which one is enabled to determine in what way the anti- 

 septic acts; that is, it must be possible to leave the antiseptic 

 to act on the micro-organisms in one case, whilst in another 

 it must be possible to get rid of the whole, or by far the 

 greater part of the antiseptic, and then see whether the 

 organism will begin to grow or not. 



(h) Another point to be attended to, is that during the 

 whole of the manipulation there shall be as little exposure 

 of the materials with which one is working as possible. 



(c.) The process should be available for use with either 

 fluid or solid media, and the results should be easily observ- 

 able and readily followed. 



The method of procedure I adopt is as follows : — Take two 

 or three dozen test-tubes of exactly the same size (I have 

 found that J-inch test-tubes 5 inches long are perhaps the 

 best) ; wash them thoroughly with a dilute acid, then with 

 ammonia, and lastly with distilled water ; allow them to dry, 

 plug them with cotton wadding in the ordinary manner, and 

 place them in the hot-air steriliser, where they should be kept 

 for an hour or two at a temperature of 150° C. to 160° C. 

 These are to be kept at hand for use as afterwards described. 



If it is wished to use a solid medium, either gelatine or 

 agar-agar may be used, J-inch test-tubes again being used. 

 The medium may be allowed to "set," with the tube in 

 either the vertical or in the sloping position as required. 



If a fluid medium is to be used, the J-inch test-tubes should be 

 partially filled (2 inches), as in the case where gelatine is used. 



Next take pieces of thin glass rod about 5 or 6 inches in 

 length, and into the end of each fuse a piece of thin platinum 

 wire about 2 inches in length, on which have been formed a 



