VESSELS OF THE CHOROID. 303 



pressions, which form the so-called reticulum of the ciliary 

 body.* This reticulum is produced by small elevations anas- 

 tomosing with one another, and enclosing depressions which 

 contain pigment. The meshes of this reticulum are smaller in 

 proportion to their distance from the ora serrata. The plexi- 

 form character of the vitreous layer is preserved as far as to 

 the iris. 



2. The vessels of the choroid, as has been already stated, 

 form two layers : the chorio-capillary layer, known also as 

 the membrana Ruyschiana, which reaches only as far as to the 

 ora serrata, and the layer composed of the larger arterial and 

 venous trunks, which has also been termed the tunica vasculosa 

 Halleri. The ramification of these vessels will be hereafter 

 separately described, but a few remarks may here be made in 

 respect to some peculiarities of their structure. 



The capillaries are so intimately connected with the vitreous 

 membrane by means of a very thin connective-tissue stroma, 

 that their separation can only be effected by the application 

 of reagents which dissolve the stroma. 



The walls of the capillaries present no points of difference in 

 their structure from the capillaries of other regions of the 

 human body. Contrary to the opinion of Henle, their walls 

 contain nuclei ; and this not only in young persons, as H. Miiller 

 admits, but also in those of advanced age. In old persons, how- 

 ever, the nuclei are somewhat atrophied, become flattened, whilst 

 at the same time the vascular walls are thickened, rendering 

 their observation more difficult. 



In many instances we see in the eyes of persons apparently in perfect 

 health elongated cells placed by the side of the capillary wall, from 

 which extremely delicate processes, visible only under the highest 

 powers, extend to the wall ; but these cells and their processes, which 

 join to form a plexus, are brought very clearly into view in inflammation 

 of the choroid. In such cases these processes extend themselves also 

 into the interspaces of the capillaries. 



The arterise ciliares breves are characterized by the great 

 development of their circular muscles. They are accompanied 



* H. Miiller, Archiv fur Ophthalmologie, Band ii., Heft ii., Anatomische 

 Beitrage zur Ophthalmologie. 



