734 



SPECIAL HISTOLOGY. 



Fig. 299. 



containing an extremely abundant capillary plexus — the memhrana 

 cJioriocajjiUaris, which, however, does not extend further in front than 

 the ora serrata. The tissue of which the proper clioroid is constituted, 

 except the vessels and nerves, which indeed make up a considerable part 

 of it, and the ciliary muscle, is of a peculiar kind, and cannot conve- 

 niently be described under any particular head, but like the fibres of 

 the lig . pcctinatum of the iris, though in somewhat different respects, is 

 intermediate between the connective and elastic tissues. In the outer 

 portions of the tunic, this stroma is formed of fusiform or stellate, very 

 irregular, and extremely pale, or more or less brown nucleated cells, 

 0-008-0-02 of a line long, which anastomose frequently with each other 

 by shorter or longer, usually very delicate (0-0005 of a line), but rather 

 rigid processes, and from their great number represent a lax membra- 

 nous tissue. There would be nothing very pecu- 

 liar in this, and these cellular networks might 

 properly be classed with other similar anasto- 

 mosing pigment-cells, as for instance in the 

 batrachian larva (most characteristic in Alytes); 

 but in the inner layers of the choroid, and espe- 

 cially in the memhrana ehoriocapillaris, they 

 gradually pass into homogeneous, nucleated tis- 

 sue, at first containing a little pigment, but after- 

 wards none at all ; and which, although in ap- 

 pearance very similar to homogeneous connective 

 tissue, is distinguished from it by its resistance 

 to acids and alkalies, and approximates the elastic tissue, from which, 

 however, it likewise differs in its trifling elasticity and paleness; whence 

 it is better, at present, to regard it as sui generis. 



The ciliary ligament of anatomists, or the musculus ciliaris s. tensor 

 chorioidece (Fig. 296 Jc), the really muscular nature of which was recog- 

 nized almost simultaneously by Brlicke and Bowman, is a tolerably 

 thick layer of radiating smooth muscular bundles, passing from the 

 most anterior border of the sclerotic upon the ciliary body, and ceasing 

 in its anterior half, opposite the part where the ciliary processes are 

 placed, internally. More precisely described, the ciliary muscle arises 

 where the sclerotic is grooved for the formation of the venous sinus of 

 Schlemm, and, in fact, from a special, dense, smooth tract (Fig. 296 Z), 

 which, forming the inner wall of the canal in question, coalesces with 

 the sclerotic, and also receives a portion of the fibrous network, into 

 which the memhrana DeJiioursii is prolonged, the fibres of which are 

 completely blended with the elements of the tract in question, and re- 

 semble the others in all respects except that they are much finer, 



Fig. 299. — Cells from the stroma o^ \\\e choroid : a, pigment-cells; 6, uncolored fusiform 

 cells; c, anastomoses of the former. Human. — Magnified 300 diameters. 



