159 — 



Results differing from each other have been obtained with the 

 following substances in the two series of experiments: — 



According 

 to Bruning 



According 

 to K. Robert 



Bitter almond oil, artificial . 



Terpinene 



Citronella oil ..... . 



Turpentine oil, ozonised 

 Turpentine oil, free from oxygen 



Dill oil 



Pine needle oil ..... 



Coriander oil 



Linalool 



Spoon wort oil, natural 

 Terpineol 



below i in 10 



below i in i o 



i in 50 to 1 in 100 



1 in 25 to 1 in 50 



1 in 25 to 1 in 50 



above 1 in 100 



above 1 in 1 00 



I in 25 to 1 in 50 



I in 1 o to 1 in 2 5 



1 in 50 to 1 in 100 



below 1 in 1 o 



1 11150 



to 1 in 1 00 



These differences in the results may be due: 1. to a difference 

 in the content of bacteria in the milk; 2. to change or decomposition 

 of the substances examined; 3. to this, that it is occasionally doubtful 

 whether the lead paper is still to be considered as blackened, or not. 



The most important divergent result of my series of experiments 

 is in my opinion the correction of Bruning's proposition, according 

 to which artificially produced substances from essential oils or oils 

 entirely artificial are said not to act identically with those separated 

 from plants. I found an equally strong action with natural 

 and with artificial mustard oil and oil of bitter almonds, 

 and the same applies to natural and to artificial oils of 

 wintergreen and spoonwort. It is possible that the difference 

 in our results is due to this, that Bruning used partly old prepa- 

 rations, that is to say preparations which may have become partly 

 decomposed. I, on the other hand, had fresh preparations placed at 

 my disposal by Messrs. Schimmel & Co. 



Of other results, I would lay stress on the following: Most ter- 

 penes have according to Bruning and myself a strikingly 

 feeble action. For this reason, the endeavours to place on the market 

 essential oils free from terpenes are fully justified, also with regard 

 to their bacteriological action. An exception is formed by limonene, 

 which even when diluted 60 times prevents the formation of sulphur- 

 etted hydrogen. It is well known that R. Kobert has introduced 

 limonene into medical practice, as a substitute for turpentine oil, for 

 inhalation in gangrene of the lung, for bronchitis putrida, and for the 



