ZOOLOGY AN 1 1 1 JOT A NY, MICROSCOPY, ETC. 



189 



into a series of U-tubes, which are then plugged and sterilized for three 

 minutes at 110° C. The toxic substances are added to the media in 

 definite proportions. When toxic substances are added in the place of 

 distilled water they are added in double strength to the content required 

 in the mixture ; thus if the toxic content needed is A per litre, a 

 solution containing 2A per litre is added, and so on. The inoculation 

 and the growth of the lactic organism in the tubes containing various 

 chemicals in solution and in the control-tubes containing distilled water 

 is arranged to take place as far as possible under identical conditions of 

 temperature, and so forth. 



The following table, which is a summary of the results obtained with 

 three different concentrations of the toxic substances (A) used, compared 

 in each case with similar experiments conducted with controls containing 

 distilled water (N), shows quantitatively the amount of lactic acid 

 produced by a ferment A (the action of a similar ferment N being in 

 each case 100) when it is allowed to actuate solutions free from or 

 containing varying quantities of the substance which produced the 

 strain A : — 



Selinate of Potash 

 Phosphate of Potash 

 Azotate of Potash . 

 Sulphate of Potash 

 Chloride of Soda . 

 Bromide of Potash 

 Arsenate of Soda . 

 Nitrate of Thallium 

 Saccharose . 



Mean . 



2A 



164 

 206 

 183 

 138 

 138 

 153 

 174 

 153 

 123 



159 



These figures prove the adaptation of the organism to the toxic 

 s id istances, and also show that a diminution of ferment activity takes 

 place when the organisms which have been accustomed to grow in the 

 presence of such toxic substances are again allowed to grow in normal 

 milk. The only exceptions to this are to be found in the cases of 

 sulphate of copper and sodium chloride. 



Testing Antiseptics.* — W. W. Cheyne, in a lecture before the Royal 

 ( 'ollege of Surgeons, stated that in co-operation with A. May, Bassett- 

 Smith and A. Edmunds, experiments had been made to test the value of 

 certain antiseptics with reference to the treatment of wounds in war. 

 The technique, in their own words, is as follows : — 



" Speaking generally, the plan which we have ultimately adopted as 

 regards agar, is to place the antiseptic paste to be tested on the bottom 

 of a Petri dish underneath a slab of nutrient agar, and to paint the 

 upper surface of the agar with an emulsion of bacteria of various kinds, 



Lancet, clxxxviii. (1914) i. pp. 419-30 (1 pi.). 



