Jeffries.] 2 [May 16, 



From George Meyer's (Med. Student in Bremen) Essay on the Comparative 

 structure of the Annuhxs ciliaris in Man and Mammals, to which a prize 

 was awarded by the Faculty of Heidelberg. R. Virchow's Archiv, Novem- 

 ber, 1865. 



The Annulus ciliaris in man is attached by a very thick fibrous net to the 

 posterior and inner wall of Schlemm's canal, and over a short space of the 

 adjacent sclerotic. The fibre bundles ruu in various directions from Schlemm's 

 canal, some as a meridional layer directly backwards, lying close against each 

 other to their insertion in the choroid, and others in a curve from outwards in- 

 wards (concavity towards centre of eye). These last bundles form numerous in- 

 tercommunications, aird divide up into several smaller ones to again unite further 

 on. There are thus formed numerous open spaces which are mostly filled with 

 Midler's circular fibres. These open spaces ai'e more frequent over the cihary 

 processes, and therefore most circular fibres are here found. These circular 

 fibres also frequently interlace; often some of the muscular bundles pass from 

 their meridional direction into a circular one. 



Prof. J. Henle's description and drawings of the ciliary muscle, 

 lately published, agree with Meyer's. In his physiological remarks 

 he considers " that the action of the circular and meridional fibres 

 mutually assist each other in increasing the thickness of the muscle." 

 He says that accommodation takes place as I have held, " produced 

 as far as we can now see by the ciliary muscle, but in what manner 

 the latter acts is still improved." 



I also stated that the annulus ciliaris or ciliary muscle differed so 

 much in animals from man that it was useless to attempt to adduce 

 from them the mechanism of accommodation in man, and had on this 

 account desisted myself. Meyer's investigations seem to bear me out 

 in this also, as will be seen from these two rough drawings of the cil- 

 iary muscle of a wild cat, and the annulus ciliaris of an antelope. 

 Meyer examined a number of different animals, still hardly enough to 

 draw a complete conclusion. His results ai'e as follows : 



The Anmihis ciliaris of the apes consists of very long contractile fibre cells. 

 Its topographical relations greatly resemble the human as regards origin, in- 

 sertion and fonn. Open spaces are rarely present in the tissue, and Miiller's 

 fibres are entii'ely wanting. 



The Annulus ciliaris of the carnivcrrous animals is muscular in character, its 

 filn-es run from before directly backward, and leave no interspaces. The cir- 

 cular muscular bundles, and the so-called intercommunicating fibres, are en- 

 tirely wanting. 



The Annulus ciliaris of the rodents is formed either of sub-scleral tissue or 

 time connective tissue; it is at any rate very insignificant, and in some hardly 

 perceptible. 



The Annulus ciliaris of the 2Mchydermata consists of connective tissue, the 

 separate bundles of which lie without interspaces so close together as to render 

 them readily mistaken for muscular fibres. The ciliary band is in them thin, 

 but extends far backwards. 



The Annulus ciliaris of the solipeds, as in the horse, consists of a fine 



