EYE AS A CAMERA OBSCURA. 320 



That the eyes of living men and women emitted light, and shone like those of 

 the cat, had been occasionally noticed and recorded from an early time, but the 

 phenomenon was supposed to be an exceptional, and indeed very rare one, and 

 was either credulously magnified into a highly marvellous occurrence, or despised 

 as of questionable accuracy, and of little real significance. In (or about) 1847, 

 however, Mr Cumming, an English medical practitioner, pointed out that the phe- 

 nomenon in question might be witnessed in every human eye, if looked for in the 

 right way ; and a little later and independently, Brucke made the same discovery 

 in Germany, through the curious circumstance, that occasionally when looking 

 through his spectacles, at the face of another, he saw his neighbour's eye glare like 

 a cat's. 



In 1851, the accomplished physiologist and natural philosopher of Koenigs- 

 berg, Helmholtz, showed how the observation which Brucke had made accident- 

 ally, might be repeated at will ; and carrying out the principle thus established, 

 constructed an eye-speculum which soon proved a most valuable addition to the 

 diagnostic apparatus of the oculist. Other eye-specula or ophthalmoscopes were 

 devised or improved by Ruete and Coccius of Leipsic, Anagnostakis of Athens, 

 and the English opticians, and are now in use in the hospitals of this country 

 and the continent. It will be sufficient for me, therefore, to give in a note, the 

 names of some of the chief works from which those to whom the subject is new 

 may obtain information regarding eye-specula ; especially as no more complex 

 instrument than a fragment of polished glass, or of perforated polished metal is 

 required to show that light is reflected from the bottom of the eye ; and even this 

 is only needed to facilitate the observation ; for by following Mr Cumming' s direc- 

 tions the fundamental phenomenon may be witnessed without the employment 

 of any reflector.* 



The demonstrability of the proposition, that the eye is not a camera obscura, 



* Cumming's observations are contained in Medico-Chir. Trans., Lond., vol. xxix., p. 283; 

 BrDcke's, in Muller's Archiv., 1847, p. 225. 



Helmholtz's desci-iption of his speculum occurs in a little work, entitled, " Beschreibung eines. 

 Augen-Spiegels zur Untersuchung der Netzhaut in lebenden Auge. Berlin, 1851." An excellent 

 abstract of this paper by Dr W. R. Sanders, accompanied by comments of his own, will be found in 

 the Edinburgh Monthly Journal of Medical Science, July 1852, p. 40. I am indebted to this gentle- 

 man for my knowledge of Helmholtz's instrument, and for the opportunity of using it. 



The eye-specula of Ruete and Coccius, as well as of Helmholtz and others, are described in a 

 work, entitled, " Bildliche Darstellung der Krankheiten des Menschlichen Auges, von Dr C. G. T. 

 Ruete ; 1 and 2 Lieferung: Leipzig, 1854." Professor Ruete's beautiful work contains a series of 

 coloured drawings, representing the internal structures of the eye, as seen under the speculum. 



Since this paper was read to the Society, a valuable communication on the medical employment 

 of eye- specula has appeared in the British and Foreign Medico-Chir. Review for April 1855 (p. 501 ) 

 It is entitled, " On the Means of Diagnosing the Internal Diseases of the Eye. By C. Bader, M.D., 

 and Bransby Roberts, Esq., Resident Medical Officer, Royal London Ophthalmic Hospital, Moor- 

 fields," and contains the fullest and most recent account of eye-specula accessible to English readers, 

 with a record of observations made on healthy and diseased eyes. From this paper, I have borrowed 

 the use of the word Ophthalmoscope, used occasionally in the text. 



