I5I2 A MANUAL OF ANATOMY 



ment-cells, supported by connective tissue. The bloodvessels are 

 arranged partly as arteries and veins, and partly as capillaries. 

 The choroid proper is therefore composed of two layers, namely, 

 external or lamina vasculosa, and internal or lamina chorio- 

 capillaris. 



The lamina vasculosa (arterio-venous layer) is composed of 

 (i) branches of the short ciliary group of the posterior ciliary 

 arteries, which pass forwards before they turn inwards to ter- 

 minate in capillaries ; and (2) veins, which form the chief part of 

 the lamina vasculosa, and are called the vense vorticosse. These 

 veins are very closely set, and are arranged in a whorled manner. 

 They ultimately converge and form about four vessels, which 

 pierce the sclerotic nearly midway between the optic entrance and 

 the comeo-scleral junction, at points equally distant from each 

 other. Scattered throughout the lamina vasculosa there are 

 branched pigment-cells. 



The lamina chorio-capillaris, or tunica Ruyschlana, is composed 

 of a plexus of capillary bloodvessels, the arteries leading to it 

 being derived from the short ciliary arteries. 



The lamina vasculosa and lamina chorio-capillaris are connected 

 by fine elastic fibres, which form what is known as the stratum 

 intermedium. 



The lamina basalis, or membrane of Bruch, is situated on the inner 

 surface of the lamina chorio-capillaris, which it separates from the 

 pigmentary layer of the retina. It is a very delicate membrane, 

 without any very definite structure. 



Tapetum. — This is present in certain animals. It lies between the lamina 

 vasculosa and the lamina chorio-capillaris in the stratum intermedium, and 

 it gives rise to a rainbow-like appearance. In some animals it is fibrous in 

 structure, and in others cellular. 



2. Ciliary Body. — The ciliary body, as stated, connects the anterior 

 part of the choroid to the circumference of the iris. It is composed 

 of (i) the orbicularis ciliaris, (2) the ciliary processes, and (3) the 

 ciliary muscle. 



The orbicularis ciliaris is a narrow zone which lies immediately 

 in front of the anterior part of the choroid, with which it is con- 

 tinuous. It presents plications which are radially disposed, and 

 it separates the ciliary processes from the ora serrata of the retina. 



The ciliary processes, which are about seventy in number, are 

 projections or infoldings of the anterior part of the choroid, and 

 consist of the choroid proper and the membrane of Bruch. They 

 constitute a series of rays, arranged in a circular manner, and 

 converge as they pass inwards and forwards to the periphery 

 of the crystalline lens on its anterior aspect. They are somewhat 

 conical in outline. Their free extremities, which are round and 

 prominent, lie behind the circumference of the iris upon the 

 anterior aspect of the periphery of the crystalline lens. Their 

 attached extremities are connected with the orbicularis ciliaris. 



