584 



NATURE 



[June 29, 191 1 



LETTERS TO THE EDITOR. 



[The Editor does not hold himself responsible for opinions 

 expressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part 0/ Nature. 

 No notice is talicn of anonymous communications.] 



New Use for Eucalyptus. 

 Thk following extract from a private letter deserves a 

 wider publicity : — 



\V. T. Tiiiselton-Dyek. 



Vou may perhaps remember the work published in 1902 

 from this institution on " Kucalypts and their Essential 

 Oils." Prior to this the eucalyptus oil industry was 

 in a chaotic state in Australia, the New South Wales 

 article being almost unmarketable. Hy working out the 

 species on a basis as laid down in the work (supra) — that 

 i>, a natural one — many new products were discovered, 

 such as geraniol, the active principle in the otto of roses ; 

 a dextro- and a huvo-turpentine corresponding to the 

 American and French respectively; many eucalyptol oils 

 (medicinal), in addition to those previously known ; citral, 

 from which ionone, the artificial perfume of violets, is 

 made; citronellal, corresponding with the product obtained 

 from the lemon grass of India ; eudesmin and other products 

 of unknown economic value at present. 



The British pharmacopoeia laid it down that no euca- 

 lyptus oil should be sold unless it contained not less than 

 50 per cent, eucalyptol, but such did not hold good for 

 Australia ; consequently any oils were sold for therapeutic 

 purposes. 



But recently, through our instrumentality, the Health 

 Board has passed a regulation that the B.P. standard 

 should obtain here ; consequently there has been a " slump " 

 in the oils thus disqualified, and so these became worthless. 

 Naturallv the distillers were very much put out with us, 

 and some travelled so far as Victoria and Queensland to 

 interview us and discuss the matter. But the hands of 

 the clock could not be put back. 



The now discarded oils have been classified by the chemist 

 as phellandrene oils, and the particular gum trees yield 

 them in larger quantity than any other oils, and the 

 desideratum was to find an industrial avenue for their 

 utilisation. Well, this is how it has come about. There 

 are at rortain large mining centres here millions of tons 

 of " tailings," containing particles of minerals very finely 

 divided, and the trouble in the past has been to extract 

 these profitably, and many methods and patents have been 

 adopted, but none satisfactorily. 



At Broken Hill, our greatest mining centre, chemical 

 investigation has been carried on for some time, and a 

 complete series of essential oils of our own extraction 

 and true to botanical names was forwarded for trial. 

 The result was that the phellandrene oils yielded from 

 8f> to 90 per cent, concentrates, the highest of any oil 

 experimented with ! Here indeed was a market. The 

 demand for these particular oils has at once enormously 

 increased ; hundreds of tons are required, for the method 

 will be introduced into U.S. .A., Canada, Queensland, and 

 through all .Australia, South Africa, and wherever the 

 industry obtains. 



Its utilisation is the essence of cheapness, and the in- 

 formation on a samole that I brought from Broken Hill 

 myself reads as follows : — Zinc concentrates ; about Zn 

 47 per cent., Pb 10 jier cent., Ag 15 oz. ; recovered by 

 eucalyptus oil 5 lb. per ton of concentrates. 



When we started out on our research on eucalypts we 

 little thought that the oil would play so important a part 

 in mining. Rich. T. Baker. 



Technological Museum, Sydney, April 7. 



made in the year ibbo by Marcello Malpighi in the cit> 

 of Bologna, and yet nearly every author gives the date of 

 this discovery as 1661. 



The latest statement of 1661 is in Prof. Miall's delightful 

 little book " The History of Biology," in which in the 

 useful chronological table we find : — • 



" 1661. Passage of blood through capillaries observed by 

 Malpighi." As justifying this date, he would doubtless 

 point to the note at the head of the table : — (" The date 

 of a discovery is the date of its first publication when that 

 is known.") 



Now while in many cases this principle may be not onI> 

 a convenient one, but the only one capable of application, 

 yet in certain cases it is a principle not to be followed at 

 all. 



These cases are those in which we have evidence regard 

 ing both the date of a discovery and the date of its being 

 made known. 



For instance, the date of the discovery of the circula- 

 tion of the blood by William Harvey is certainly earlier 

 than 1628, the date of its publicatiOVi. 



We have the evidence of Harvey's own lecture notes, 

 dated 1616, that he knew of the circulation and was teach- 

 ing it at least twelve years before he published it. Only 

 when we cannot find the true date of a discovery should 

 we fall back on the date of its publication. 



Now the discovery of the existence of the invisible 

 capillaries was a very great thing, and it seems a pity 

 that we should get into the habit of assigning it to one 

 year later than it actually was made. 



Sir Michael Foster's account in his " Lectures on the 

 History of Physiology " is clearness itself. Speaking of 

 Malpighi, we read : — " Here " (Bologna) " he resumed 

 office as a Professor of Medicine, and in spite of domestic 

 troubles and anxieties, pursued his researches to such good 

 effect that he was able in the next year, 1660, to announce 

 privately to Borelli his discovery of the structure of the 

 lung, an account of which was published in the year 

 following." 



The published account alluded to is his " De pulmonibus 

 observationes anatomic.-c," which, after the manner of th*- 

 time, is in the form of two letters to his friend G. A. 

 Borelli, at Pisa. 



In the second epistle he describes the circulation in the 

 herniated lung of the living frog. He heads the descrip- 

 tion with these words, " Magnum certum opus oculis 

 video" — " I see with my eyes a great, certain thing," not. 

 as always translated, " a certain great thing," which is 

 much feebler and not a true translation. 



1660. then, and not 1661, was the date of the discovery 

 of the blood-capillaries, within only three years of the death 

 of Harvey in 1657. Harvey made their existence a logical 

 necessity; Malpighi made it a histological certainty. .\s w- 

 still speak of the " rete mirabile Malpighii " — for no lapse 

 of time can ever make that rete less wonderful — we rnight 

 as well take the trouble to assign the discovery of it to 

 its correct date, 1660. D. Fraser Harris. 



The University, Birmingham, June 19. 



The Date of the Discovery of the Capillaries. 



The discovery of the capillary' blood-vessels being an 

 event of such supreme importance in biology, it is highly 

 desirable that the date of it should be accurately asrcr- 

 tained. It so happens that it is known for certain it was 



NO. 2174, VOL. 86] 



The Osmotic Pressure of Colloidal Salts. 



Congo red and similar salts in aqueous solution cannot 

 diffuse through an ordinary dialysing membrane. When 

 the osmotic pressure is directly measured by an osmometer 

 it is found to be about that which the kinetic theory would 

 ascribe to the salt present if the molecules were completel} 

 un-ionised. 



The solutions, on the other hand, are good conductor- 

 of electricity, and the specific molecular conductivity of 

 the solutions employed is that of a solute 60 to 70 per 

 cent, of the molecules of which are dissociated. There i- 

 thus, as Bavliss has pointed out,' an apparent conflicr 

 between the results obtained by different experimental 

 methods. 



Congo red is the sodium salt of a complex organic acid. 

 Its ions, therefore, are of very unequal size, and as the 

 membranes employed in the osmometer are permeable to 



' Paper read a» the meet"ng of the Biochem'cal Society, May 4. 



