AND THEIR ESSENTIAL OILS. 7 



The occurrence of the terpene phellandrene in the oils 

 of a majority of the species is a character of some import- 

 ance, and one which may eventually be shown to have some 

 significance in determining distribution of species. 



The oil of E. Risdoni is specially worthy of mention, 

 because of the large amount of eucalyptol which occurs in 

 it, together with phellandrene. It has latterly been the 

 practice in England, America, and in Europe to demand 

 oils rich in eucalyptol (cineol) for pharmaceutical purposes, 

 and the presence of phellandrene has been looked upon 

 with considerable disfavour. But when we consider that 

 the medicinal value of Eucalyptus oil was first determined 

 on oils of the " amygdalina " group, even including that 

 of E. dives (in which eucalyptol is almost absent), it may 

 be that the present condemnation of a phellandrene-bear- 

 ing oil like E. Rixdom is hardly warranted, and is per- 

 haps, at the least, injudicious. Dr. Cuthbert Hall, of 

 Parramatta, in 1904, showed that eucalyptol when pure 

 had very little antiseptic power much less than that of 

 many other constituents of Eucalyptus oils, including 

 phellandrene. Dr. Martindale has also recently shown 

 that eucalyptol has very weak antiseptic power in com- 

 parison with many other substances. Piperitone, a constit- 

 uent of the oils of the "Peppermint" group, was shown 

 by Dr. Hall to be very energetic in its action, and this is 

 a constant constituent in the oils of E. amygdalina, 

 and E '. Risdoni. Perhaps, however, the efficacy of Euca- 

 lyptus oil is more largely due to the mixture of constituents 

 than to the action of the constituents themselves when 

 these are isolated in a pure condition. Certainly all is not 

 yet known about the therapeutic value of Eucalyptus oils, 

 and the present official conclusions in this respect appear to 

 us to have been based on insufficient experimental data. 

 Bearing in mind, however, the reputed efficacy of the other 

 constituents, it might be well to insist on a minimum of 50 

 per cent, of eucalyptol in any Eucalyptus oil to be used 

 for pharmaceutical purposes, and we do not, for several 

 reasons, suggest a less amount. If this standard is eventu- 

 ally arrived at, and phellandrene not condemned, then E ' . 

 Risdoni would be a very good species to exploit for its oil. 

 The volatile aldehydes in the oil of this species are small in 

 amount and are not at all objectionable. The above 

 remarks apply in a lesser degree to the oil of E '. linearis. 

 If oils similar to E '. Risdoni are eventually recognised offi- 

 cially, it would be necessary to reduce the standard for 

 specific gravity to 0'905 at 15 C. 



