I02 



NATURE 



[May 31, 1900 



LETTERS TO THE EDITOR. 



£ The Editor does not hold himself responsible for opinions ex- 

 pressed by his correspondents. Neither can he undertake 

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

 manuscripts intended for this or any other part of Nature. 

 No notice is taken of anonymous communications. "[ 



A. Third Specimen of the Extinct " Dromaius ater," 

 Vieillot; found in the R. . Zoological Museum, 

 Florence. 



In January 1803, a French scientific expedition, under 

 Baudin, visited the coast of South Australia and explored 

 Kangaroo Island, called by them " Isle Decr^s." One of the 

 naturalists attached to the expedition was the well-known 

 F. Peron, who wrote an interesting narrative thereof. He 

 noticed that Decres Island was uninhabited by man, but, 

 although poor in water, was rich in kangaroos and emus 

 {Casoars he calls the latter), which in troops came down to the 

 shore at sunset to drink sea-water. Three of these emus were 

 caught alive, and safely reached Paris; we learn from the 

 " Archives du Museum " that one was placed in the Jardin des 

 Plantes, and two were sent to " La Malmaison," then the resi- 

 dence of the Empress Josephine. We learn later that two of these 

 birds lived to 1822, when one was mounted entire and placed in 

 the ornithological galleries of the " Museum," the other was 

 prepared as a skeleton and placed in the comparative anatomy 

 collections. No mention is made of the ultimate fate of the 

 third specimen. 



Peron was unaware that the emu he had found on the 

 Kangaroo Island was peculiar and specifically quite distinct from 

 the New Holland bird ; this was found out much later, and too 

 late ; for after Peron and his colleagues no naturalist evermore 

 set eyes on the pigmy emu of Kangaroo Island in its wild 

 condition ! It appears that when South Australia was first 

 colonised, a settler squatted on Kangaroo Island and systematic- 

 ally exterminated the small emu and the kangaroos. When the 

 interesting fact was ascertained that Peron's emu was a very 

 distinct species quite peculiar to Kangaroo Island and found 

 nowhere else, Dromaius ater had ceased to exist ; and the only 

 known specimens preserved in any museum were the two 

 mentioned above, in Paris. 



For some years past my attention had been drawn to a small 

 skeleton of a RatitK in the old didactic collection of the 

 R. Zoological Museum under my direction ; it was labelled 

 " Casoario," but was in many ways different from a cassowary ; 

 but other work kept me from the proposed closer investiga- 

 tion, and it was only quite recently, during a visit of the 

 Hon. Walter Rothschild, on his telling me that he was 

 working out the cassowaries, that I remembered the enigmatical 

 skeleton. A better inspection showed us that it is, without the 

 least doubt, a specimen of the lost Dromaius ater. I afterwards 

 ascertained that it had been first catalogued in this museum in 

 1833 ; that most of the bones bore written on them in a bold 

 round hand, very characteristic of the first quarter of the 

 nineteenth century, the words " Casoar male ; " and lastly, that 

 during the latter part of Cuvier's life, about 1825-30, an 

 exchange of specimens had taken place between the Paris and 

 the Florence Museums. I have thus very little doubt that our 

 specimen is the missing third one brought alive to Paris by 

 Peron in 1804-5. 



This highly interesting ornithological relic is now on loan at 

 the Tring Museum, and can be seen- there by any ornithologist 

 in England who may wish to examine it. I intend shortly to 

 give a fuller notice of this valuable specimen. 



Henry H. Giglioli. 



R. Zoological Museum, Florence, May 15. 



Chlorophyll a Sensitiser. 



It was with a feeling of great satisfaction that I read the 

 concluding lines of Dr. H. Brown's highly interesting presi- 

 dential address (Nature, September 14, 1899). I was glad to 

 see that this distinguished chemist, to whom the physiology of 

 plants is so much indebted, adopts certain views on the chloro- 

 phyll function, which I have been defending for more than a 

 quarter of a century against the leading authorities of the German 

 Physiological School (Sachs and Pfeffer). But since some slight 

 errors seem to have crept into Dr. Brown's statements of my 

 opinions on the subject, I may, perhaps, be allowed to bring 

 forward the following corrections. 



NO. 1596, VOL. 62] 



Dr. Brown seems to believe that the analogy between the 

 action of chlorophyll and that of a chromatic sensitiser was 

 "first pointed out by Captain Abney" and "more fully 

 elaborated " by me ; and secondly, that I give "a far too simple 

 explanation of the facts" by admitting a " me)-e physical ixz.x\s- 

 ference of vibrations of the right period from the absorbing 

 chlorophyll to the reacting carbon dioxide and water." 



To begin with the less important question of priority, I must 

 confess that up to this date I am not aware of Captain Abney's 

 claims. Had I known them, I should have been the first to 

 acknowledge my debt to that accomplished investigator, whose 

 brilliant achievements in this line of research I have never omitted 

 to admire. The fact that the dissociation of the carbon dioxide in 

 the green leaf is affected by the rays of light absorbed by 

 chlorophyll was for the first time established by my researches 

 in 1873, and an account of these experiments presented to the 

 International Congress of Botany in Florence (May 1874).^ 

 At the same date (1873) Prof. H. Vogel made his important 

 discovery of the chromatic sensitisers, and in November 1875, 

 E. Becquerel applied it to the chlorophyll-collodion plates. In 

 May 1875 appeared my Russian work on the chlorophyll 

 function, of which the French article ^ in the Annates de Chimie 

 et de Physique of 1875, as expressly stated, is but an extract. 

 In this French translation the idea that chlorophyll may be 

 considered as a sensitiser is fully discussed. Consequently any 

 claim of priority may be fairly advanced, only in favour of a 

 paper having appeared in the short interval of a year — from 

 May 1874, when I announced the fact, to May 1875, when I 

 interpreted it in the light of H. Vogel's recent discovery. On 

 consulting the R. S. Catalogue of Scientific Papers, I could not 

 find any paper of Captain Abney's for this period 1874-1875.* 



So far concerning the priority question. Passing to the second 

 point, I am sorry to say Dr. Brown is decidedly in the wrong, 

 for in my French paper just cited, and which probably escaped 

 his notice, after discussing the quite recent discoveries of H. 

 Vogel and Edmond Becquerel, I conclude : " Ou ne saurait 

 pour le moment decider la question de savoir si cet effet serait 

 du uniquement a un phenomene physique, ou bien si la matiere 

 colorante prendrait part a la transformation chimique. Cette 

 derniere maniere de voir ferait rentrer I'action de cette matiere 

 (chlorophylle) dans la regie generale de Taction acceleratrice des 

 matieres organiques dans les reactions photochimiques, car c'est 

 generalement en absorbant les produits de la dissociation, 

 effectue par la lumiere, que les substances organiques detruisent 

 cet equilibre qui tend a s'etablir entre le corps decompose et les 

 produits de decomposition et c'est ainsi qu'une dissociation 

 partielle aboutit a une decomposition complaite."* At a later 

 date, in a report presented to the International Congress of Botany 

 in St. Petersburg (1884), taking in account -the subsequent 

 photographical work on the sensitisers, I brought forward 

 experimental proof that chlorophyll may be considered a sensi- 

 tiser in Captain Abney's sense of the word : " La chlorophylle 

 est un sensibilisateur regenere a mesure qu'il se decompose et 

 qui provoque en eprouvant une decomposition partielle la de- 

 composition de I'acide carbonique." ^ 



From all these quotations it may be inferred that I always 

 kept in view the chemical aspect of the chlorophyll function, 

 now advocated with such stress by Dr. Brown." 



But I did not content myself with such purely theoretical 

 considerations, and ever since have been in search of what Dr. 



1 Atii del Congresso Botanico teniito in Firenze, 1S75, p. 108. At a 

 still earlier date {Botanische Zeititng, 1869, No. 14), I found out the source 

 of T. W. Draper's error, and proved that the process is chiefly due to the 

 red rays of light. 



^ " Recherches sur la decomposition de I'.icide carbonique dans le spectre 

 solaire par les parties vertes des vegetaux " (Extrait d'un ouvrage " Sur 

 I'assimilation de la lumiere par les v^getaux," St. Petersbourg, 1B75, public 

 en langue Russe)/4»Ka/^j de Chimie et de Physique, 5 serie, t. xii. 1877. 



» Prof. Pfeffer, in his account of the whole subject (" Pflanzenphysiologie." 

 Z«eite Auflage, pp. 325-341), goes so far as to attribute this sensitiser theory 

 of the chlorophyll function to Prof. Reinke, whose paper appeared ten years 

 later. 



■» L.c. p. 40. In a footnote I add that certain physiological facts seem 

 to agree with this point of view. 



5 " ittat actuel de nos connaissances sur la fonction chlorophyllienne" 

 (^Annates des Sciences Natiirelles Botanigm, 1885, p. 119). 



6 At a still earlier date (in a Russian work on the "Spectrum Analysis 

 of Chlorophyll." St. Petersburg, 1871) I even expressed Dr. Brown's 

 present point of view in the form of an equation : 



X0 + C02=XC0 + 0.. 

 4-H3O 



=XO-fCH20-l-02 

 X being Dr. Brown's hypothetical " reduced constituent of chlorophyll.' 



