HELMHOLTZ IN KONIGSBERG 



pied the fundus of the eye. Behr, in 1839, met 

 with a case in which the iris was absent, in which 

 there was luminosity, and noted that the eyes of 

 the observer must regard those of the patient in a 

 direction nearly parallel to that of the incident rays j 

 such was also the basis of Briicke's method of observ- 

 ing the ocular light. In the case of absence of the 

 iris, the luminosity was not marked when the retina 

 was strongly illuminated. Accommodation was im- 

 perfect in such a case. 



Finally W. Gumming 1 and Briicke, in 1847, found, 

 independently of each other, the method of rendering 

 the normal human eye luminous, when the observer 

 looks at it in a direction nearly parallel to the incident 

 rays. Briicke had already applied his method to the 

 eyes of animals furnished with a tapetum. At last, 

 Wharton Jones, in 1854, writes that Charles Babbage 

 had shown to him, about the same time, a silvered 

 mirror from which a small portion of the foil had been 

 removed, by which light could be thrown into the eye, 

 and at the same time the observer could look at it 

 through the opening. This description applies well to 

 the ophthalmoscope of Coccius, but as Babbage does 

 not appear to have used lenses with his mirror, he 

 could not, in the opinion of Helmholtz, clearly see 

 the retina, and probably, for that reason, he did not 

 publish the discovery. It is evident, however, that 

 Babbage almost invented the ophthalmoscope. 



1 Medico-Chirurgical Trans., vol. xxix., p. 284. 



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