HELMHOLTZ IN KONIGSBERG 



structures, the cornea and lens, are not the same), may 

 all be determined. The invention of the instrument 

 was a new era, not only for ophthalmology, but also 

 for practical medicine, as the retina may be regarded 

 as an outlying portion of the brain ; an examination 

 of the fund us of the eye often gives the physician 

 information as to pathological changes occurring in 

 the nerve centres. Thus it is of service in the diag- 

 nosis of inflammatory actions in the brain, both acute 

 and chronic ; of changes in the meninges, or brain 

 coverings ; in locomotor ataxia ; in the various forms 

 of Bright's disease ; and many other maladies. 



The retina presents to the observing eye the ap- 

 pearance of a red-coloured concave disc with a whitish 

 oval spot to the inner side, where the optic nerve 

 enters, from which we see branching the retinal 

 vessels, the veins being darker in colour than the 

 arteries, and in the visual axis lies the yellow spot, 

 which is the most sensitive part of the retina. The 

 vessels of the fovea centralis, a minute depression in 

 the centre of the yellow spot, are so fine as to be 

 invisible to the naked eye. 



When von Graefe first saw the fundus of the living 

 human eye, with its optic disc and blood vessels, his face 

 flushed with excitement, and he cried, * Helmholtz has 

 unfolded to us a new world ! What remains to be dis- 

 covered ? ' Before the invention of the ophthalmoscope, 

 diseases of the fundus, and even disturbances of refrac- 

 tion and accommodation of the most diverse character, 

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