300 TUNICA VASCULOSA, BY PROF. A. IWANOFF. 



and anteriorly at the point of transition of the sclerotic 

 into the cornea (annular tendon of the circular muscle). These 

 two coats are elsewhere connected by arteries and nerves, 

 which perforate the sclerotic in order to enter the choroid, and 

 by veins Avhich pass in the opposite direction. 



The external surface, which is turned towards the sclerotica, 

 is of fibrous structure, and brownish colour ; where the choroid 

 is attached in front to the sclerotica, there is an annular grey 

 thickening, having a breadth of from three to four millimeters, 

 which encircles the anterior part of the vascular membrane, 

 and is termed the ciliary muscle. 



The internal surface of the choroid looks towards the retina, 

 and is very loosely connected with it as far as the ora serrata, 

 though sufficiently firmly to cause the whole external layer 

 of the retina (namely, the pigmented epithelial layer) to remain 

 adherent to it in the greater number of cases, which has led to 

 the belief that this layer belongs to the choroid. Starting from 

 the ora serrata, these membranes are much more intimately 

 united, since from this point forwards the pigmentary layer, 

 forming a bond of union between the ciliary portion of the 

 retina and the choroid; increases considerably; on which ac- 

 count also the separation of the retina from the choroid at this 

 spot does not always, and then only partially, take place. If 

 the pigment be removed, the inner surface of the choroid, as 

 far as to the ora serrata, appears perfectly smooth, and of a 

 grey colour ; behind the ora serrata its surface becomes rough, 

 and in front of it is a series of folds, arranged in a meridianal 

 direction, and separated from one another by deep furrows, 

 which are the so-called ciliary processes. 



The ciliary processes, from seventy to eighty in number, 

 have the aspect of a regularly plaited frill, and as they project 

 more and more anteriorly their apices ultimately reach the 

 ciliary border of the iris. The entire internal surface and all 

 the folds as far as their anterior margin, are covered with a 

 thick layer of pigment and with the cells of the ciliary portion 

 of the retina (pars ciliaris retinae). 



The anterior part of the choroid, commencing from the ora 

 serrata, together with the ciliary processes and the ciliary 

 muscle, are collectively termed the corpus ciliare. 



