478 



NA TURE 



^^March 29, 1877 



Boll avait dvidemment entrevu toutes ces consequences, 

 at jl eut dte de bon gout, nous semble-t-il, de lui laisser le 

 temps de les derouler k I'aise. C'est done sans droit que 

 nous voyors dej^, des k present, la presse parler, k propos 

 de ce fait, des ' ddcouvertes de MM. Boll et Kiihne' et le 

 nom de ce dernier associd a celui du seul invefiteur. 



" Deux gamins suivaient un trottoir ; I'un d'eux sif- 

 flaient un air, dont il n'etait qu'k la moitie, quand le 

 second se mit h la continuer : ' Une autre fois,' lui dit le 

 premier le regardant tres mdcontent, * tu voudras bien 

 commencer toi-meme.'" 



If I quote the above sentences it is to show that they 

 are as much opposed to truth as they are to the interests 

 of science, or as they are repugnant to good taste. 

 When a scientific man has published a discovery it is to 

 the interest of the scientific world that all who will or can 

 should be at liberty to repeat the experiments or observa- 

 tions which led to it ; if other great discoveries are made 

 by the new labourers it is to the interest of science that 

 they be published. 



In the particular case in point it would appear that 

 Prof. Boll re- discovered (and, what is more, appreciated 

 the full value of) a fact which had really been observed 

 by some others (Ley dig in 1857, and Max Schultze in 

 1866), but which had certainly not become part and 

 parcel of the common stock of scientific knowledge, viz., 

 that the rods of the retina are red, he observed that 

 under the circumstances of his own experiments the colour 

 faded at death, and arrived at the false conclusion that 

 the colour was a function of the vital condition of the 

 retina. He, however, observed the remarkable action of 

 light in modifying the colour. " During hfe," he 

 announced in his paper, " the peculiar colour of the 

 retina is continually being destroyed by the light which 

 penetrates the eye. Diffuse daylight causes the purple 

 tint of the retina to pale. The more prolonged, dazzling 

 action of the direct rays of the sun entirely destroys the 

 colour of the retina. In darkness the intense purple 

 colour is again restored. This objective alteration of the 

 peripheral structures of the retina brought about by the 

 rays of light undoubtedly occurs in the act of vision." 

 This was the great discovery which Boll made, and with 

 which his name will ever remain honourably connected. 

 Although, however, he had been in full possession of the 

 facts in the month of June of last year, when he demon- 

 strated them to Professors Du Bois-Reymond and 

 Helmholtz, and only published his paper in November, 

 he did not succeed in making the discoveries with which, 

 justly, the name of Kiihne is now associated. Kiihne 

 showed that if the retinal purple is usually destroyed at 

 death, the result is attributable to the action of light, per- 

 sistence of the colour being by no means necessarily 

 connected with the living condition of the retina. In his 

 beautiful and far-seeing discovery of the true function of 

 the retinal epithelium cells as restorers of the vision 

 purple, he was fortunate enough to make a discovery 

 which it would be very bold for any one — even for Prof. 

 Boll— to say he would have made, had time and oppor- 

 tunities been granted. In saying that Boll had dis- 

 covered everything referring to the vision -purple, M. 

 Warlomont shows that he has not appreciated the fact 

 that two great discoveries have been made, the second 

 supplementing the first, and actually needed in order that 

 the significance of the first should be appreciated. 



But I trust that the readers of Nature do not think 

 that I wish to depreciate the researches of Prof. Boll 

 whilst I act as the champion of one who needs no cham- 

 pion, seeing that he illustrates in himself the truth of the 

 adage, " le grand mdrite est toujours probe." 



Prof. Boll must reflect that great discoveries are rarely 

 completed by one man, and that it is no shame, and 

 should be no cause of sorrow, to the true man of science, 

 if the conception which he has tried to develop and 

 which he has almost raised to the position of a truth by 



his own work, receives its final development through the 

 strivings of a fellow-worker. 



Abandoning the polemical discussion upon which I felt 

 myself almost compelled to enter, I would give an ac- 

 count of the most recent results obtained by Kiihne on 

 the " Vision Purple," and published by him in the Cen- 

 tralblatt fiir die medicinischen Wissenschaften for March 

 17 (No, 11). 



The purple colour of the retina is now shown to depend 

 upon the presence of a substance which can be dissolved 

 and separated in the solid form. The only solvent of the 

 vision-purple as yet known is bile, or a pure glyko-cholate. 

 The filtered, clear solution of the vision-purple is of a 

 beautiful carmine-red, which, when exposed to light, 

 rapidly assumes a chamois colour, and then becomes 

 colourless. As long as it is at all red the solution absorbs 

 all the rays of the spectrum, from yellowish-green to violet, 

 allowing but little of the violet, but all the yellow, orange, 

 and red rays to pass. Accordingly, bloodless retinas 

 spread out and placed in the spectrum, between green and 

 violet appear grey or black. 



Kiihne has exposed retinae in different parts of a spec- 

 trum (obtained by allowing the sun's rays between eleven 

 and one o'clock to fall through a slit 0*3 mm. wide upon 

 a flint glass prism) in which Fraunhofer's lines were 

 shown in great number and with great distinctness, and 

 he has ascertained that in the yellowish green and green 

 regions the vision-purple is bleached most rapidly ; the 

 action is less in the bluish green, blue, indigo, and violet ; 

 it is still perceptible in the orange and yellow, but not in 

 the red or ultra-violet regions. 



March 24 ARTHUR Gamgee 



OUR ASTRONOMICAL COLUMN 

 The Cape Astronomical Results, 1871-1873.— Mr, 

 Stone has just circulated the results of meridional observations ot 

 stars made at the Royal Observatory, Cape of Good Hope, ia 

 the years 187 1- 1873. His present object has been not so much 

 to furnish extremely accurate places of principal southern stars 

 as to supply reliable positions of stars down to the seventh 

 magnitude within 15" of the South Pole, and it is considered 

 that this volume contains all Lacaille's stars in this region of the 

 sky, and very nearly all sevenths'not observed by him. It is the 

 *' first published instalment of the materials collected for the 

 projected Catalogue." The separate results for mean R. A. and 

 N. P.D. are given, with catalogues of places for the commence- 

 ment of each year, the whole number of stars observed being 

 about 1,400. Bessel's reduction constants are appended. This 

 form of publication is perhaps sufficiently ample in the present day, 

 though Mr. Stone alludes to a desire expressed by some astro- 

 nomers to see the Cape observations printed In detail in the same 

 manner as the Greenwich observation?, a plan hardly prac- 

 ticable with the limited staff at his disposal, and which would 

 involve very slow progress of the work with the resources of the 

 Cape press. We are inclined to think that Mr. Stone exercises 

 a wise discretion in limiting his volume to its present form, and 

 thus assuring its comparatively early distribution in the astro- 

 nomical world. As it is the volume is not produced without a 

 considerable expenditure of time in the routine work of the 

 reductions by the director himself. 



Variable Stars. — Mr. J, E. Gore, of Umballa, writes with 

 reference to several stars which may prove to be variable : — 

 (i) Lalande 140S8 (Canis Major) ; this star was observed by 

 Lalande, March 2, 1798, but the magnitude was not registered. 

 It is marked of the ninth magnitude only on Harding's Atlas, 

 but at the beginning of February in the present year Mr. Gore 

 found it a little brighter than the sixth magnitude Lalande 1410J 

 closely south of it, and "decidedly reddish." Argelander 

 served this star on December 23, 1852, and rated it 6 m, H 



