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leave the margin of the cornea, break np into two principal 

 sets or bundles of fibres, on the one hand diverging as 

 they expand into the ciliary muscle (o), and on the other con- 

 verging as they pass into the radiating tissue of the iris. 

 The primary fasciculi are crossed at right angles superficially 

 or externally, and thus bound down by a stout circlet of un- 

 striped muscular fibres [h), corresponding with the inner wall 

 of the circular sinus (s) , or the space apparently contrived 

 to permit of the play of this annular muscle. 



The fibres are flat and band-like, and difler essentially 

 from the tomentose or flaxy tissue composing the principal 

 mass, if not the whole, of the radiating bundles, both of the 

 iris and the ciliary muscle, which latter is decidedly a 

 problematical structure, more especially when the light of 

 comparative anatomy is brought to bear upon it. Thus, 

 while it is present with the same histological characters in 

 the eye of the owl (Surnia), for example, it is superimposed 

 by veritable striped muscle, taking its origin from the inner 

 fibrous surface of the cartilaginous and bony sclerotic. There 

 may possibly be some organic muscular fibres associated 

 with it, but doubtless the great mass of it is of a very difierent 

 nature. 



Immediately behind the circidar muscle above described, 

 some accessory fibrous bundles (r) pass outwards and back- 

 wards to the posterior boundary of the circular sinus, where 

 they are incorporated Avith the sclerotic. These were first 

 noticed by Mr. Bowman, and their office would appear to be 

 to keep the ciliary ligament and fore part of the choroid in 

 relation with the sclerotic during the action of the circular 

 muscle. It is probable, also, that in man they only form 

 the rudiment of that more important structure in the bird, 

 with which the striped voluntary muscle is connected an- 

 teriorly. 



Just within the attached margin of the iris the fibrous 

 tissue is supplemented by a circular framework of stout- 

 branched and reticulate yellow elastic element, essentially 

 diff'erent from that occurring in other parts of the human 

 body. This remarkable structure, acting through the 

 medium of the radially disposed wavy tissue in connec- 

 tion with it, both sheathing the vessels and running in 

 the intervening spaces, is the mechanical antagonist of the 

 sphincter fibres of the iris. It thus fulfils an office, ana- 

 logous to that of the ligamentum nuchse in browsiug animals, 

 substituting and relieving muscular action, and obviating 

 the necessity of so nice a proportion as should otherwise 

 exist between the complementary contx-actions and relaxa- 



