HELMHOLTZ IN KONIGSBERG 



the movements chiefly to the iris. This muscular 

 structure contains both circular and radiating fibres. 

 As a matter of fact, distinct radiating fibres cannot 

 be seen in microscopical preparations. Suppose both 

 circular and radiating fibres contracted simultaneously, 

 then, according to Cramer, the circular fibres offered 

 resistance to the contraction of the radiating fibres, 

 and thus the parts of the lens behind them, that is 

 near the margins, were compressed, while the central 

 part of the lens, meeting with no resistance behind 

 the pupil, was pressed forward. Donders next 

 attached importance to the fringe of elastic tissue 

 on the inner wall of the canal of Schlemm, from which 

 both the fibres of the iris and of the ciliary muscle 

 appear to originate. The latter muscle is a fringe 

 of muscular tissue, the fibres of which radiate back- 

 wards, and are attached to the ciliary processes of the 

 choroid or vasculo-pigmentary coat of the eye. It 

 lies near the zonule of Zinn, and was at one time 

 termed corpus ciliare^ the ciliary body. Briicke de- 

 scribed it in the following words : c The muscle is 

 very easy to find, as it is nothing else than the light 

 grey ring which one finds on the outer surface of 

 the anterior part of the choroid after separation of 

 the sclerotic, and which has up till now played so 

 unhappy a part in anatomy under the names of 

 ligamentum ciliare^ orbicularis ciliaris y circulus allans, 

 ganglion ciliare, etc.' It may now be well named the 

 tensor choroidei, or, as Donders suggests, the ?nusculus 

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