THE CHOROID COAT. 301 



The anterior part of the choroid has long had a special name applied 

 to it. Thus, Vesalius named it the tunica ciliaris, and subsequent 

 anatomists distinguished in this tunica ciliaris a pars plicata and a 

 pars non plicata. Fallopius was, however, the first who applied the 

 term corpus ciliare to this part of the choroid. Henle only names the 

 most anterior part of the choroid the corpus ciliare, including under 

 this term the ciliary processes and the ciliary muscle. . The zone 

 lying between the ora serrata and the corpus ciliare he terms the 

 orbiculus ciliaris, without maintaining, however, that any well-defined 

 line can be drawn between the corpus ciliare and the orbiculus ciliaris. 

 Under the name corona ciliaris, Luschka describes that portion of the 

 membrane which is connected with the zonula Zinnii, and extends from 

 the ora serrata to beyond the margin of the lens ; the ciliary muscle 

 he names the annulus ciliaris. We believe that it would be of advan- 

 tage in facilitating the comprehension of the ordinary terminology to 

 keep to one system of nomenclature, even if this did not express all the 

 anatomical peculiarities of this part of the choroid. We have selected 

 the term corpus ciliare, not because we consider it to be the best, but 

 because it is most generally employed ; in this sense Kolliker uses the 

 term corpus ciliare in his Manual, as well as H. Miiller in all his 

 treatises on the eye. 



The vessels form the chief constituent of the choroid, and on 

 this account this membrane has from a remote period been 

 considered to exert a powerful influence on the nutrition of 

 the eye. Its rich -supply of vessels explains also, without 

 doubt, the very important part it plays in the various patho- 

 logical processes taking place within this organ. 



The smooth muscles form another constituent of this mem- 

 brane, playing an important part in the functions of the eye. 

 The larger part of them is accumulated in the corpus ciliare, 

 but they are by no means altogether absent in the posterior 

 segment of the choroid. 



Lastly, the choroid is abundantly supplied with nerves. 



All these constituents are connected together by a stroma, 

 characterized by the presence of a large number of stellate pig- 

 ment cells. 



The five following layers are usually distinguished in the 

 choroid the pigment layer ; the vitreous layer ; the membrana 

 chorio-capillaris ; the layer formed by the larger arteries and 

 veins ; and lastly, the membrana supra-chorioidea. The history 



