512 THE SOLIDS. 



These laminae may be designated in general terms sepa- 

 rately as arterial and venous : the inner or arterial lamina, 

 known as the tunica Ruyschiana, consists of a dense and 

 beautiful plexus of vessels, which are so closely applied to 

 each other as scarcely to leave any intervening spaces or 

 meshes. (See Plate LX VII. Jig. 4.) The main arteries which 

 supply this tunic, and the veins which carry off its blood, 

 leave it by numerous points on its outer surface only ; the 

 veins are particularly large and numerous, and disposed in 

 beautiful curves, whence they are called vencR vorticosce. (See 

 Plate LXVIII. fig. 2.) Before leaving the choroid they 

 converge to form four or five principal trunks which enter 

 the schlerotic ; the arteries, fewer in number and much smaller 

 in size, run between the veins. 



An immense number of granular nuclei are visible in the 

 walls of the venae vorticosae. 



Stellate choroidal epithelium. Such is the distribution of 

 the blood-vessels of the choroid: the next most important 

 element in its constitution are the pigment cells ; these exist 

 in vast quantities and make up much of its substance ; they 

 are of various forms and sizes ; but being furnished with two, 

 three, or more arms or radii, they may be aptly termed stel- 

 late. The nucleus in each cell is large and particularly clear, 

 appearing almost like a hole in its centre : this is owing to 

 the absence of the colouring matter contained in each cell 

 in that situation. 



The existence of the stellate form of pigment cells in the 

 human subject appears to have been generally overlooked : it 

 was described and figured in Parts 7 and 8 of the Microscopic 

 Anatomy published in February and March, 1847, and its 

 arrangement in rows was at the same time pointed out ; its 

 position in the choroid, as well as its structure, have since 

 been examined with more care, and with the following re- 

 sults. 



This pigment is situated beneath the tunica Ruyschiana, 

 and in the intervals between the venae vorticosae, which it 

 accurately fills up, some of the arms of the cells, as well as 

 occasionally a few of the scattered cells, intrenching upon 



