812 



THE OKGANS OF SENSE. 



destitute of muscular tissue, are superficial to the arteries ; they are surrounded 

 by perivascular lymph sheaths and converge to form whorls, which open into the 

 vense vorticosae. In the tissue between the blood-vessels are numerous stellate, 

 flattened, and pigmented cells. 



The lamina choriocapillaris is composed essentially of small capillaries, which 

 form an exceedingly close network, embedded in a finely granular or almost 

 homogeneous tissue. 



The intermediate stratum between the lamina vasculosa and lamina chorio- 

 capillaris consists of a network of delicate elastic fibres and contains almost no 

 pigment cells; it is lined, next the lamina choriocapillaris, with a layer of 

 endothelium. 



The lamina basalis is transparent and nearly structureless. Its outer surface 

 exhibits a trellis-like network of fibres which unite it to the lamina choriocapillaris, 

 while its inner surface is smooth and is in contact with the pigmented layer of the 

 retina. 



Tapetum. In many animals a brilliant iridescence is seen on the postero-lateral part of 

 the chorioid ; to this the name tapetum is applied. Absent in man, it may be due, as in the 

 horse, to a markedly fibrous condition of the stratum intermedium (tapetum fibrosum), or as 

 in the seal, to the presence of some five or six layers of flattened iridescent cells lying imme- 

 diately outside the lamina choriocapillaris (tapetum cellulosum). 



Corpus Ciliare. The ciliary body connects the chorioid to the circumference 

 of the iris (Fig. 683), and comprises three zones, viz. : (a) the orbiculus ciliaris, 



(&) the ciliary processes, 

 and (c) the ciliary muscle, 

 -ins The orbiculus ciliaris 



is a zone of about 4 mm. 

 in width immediately 

 adjoining the chorioid ; 

 it exhibits numerous 

 radially arranged ridges. 

 Processus Ciliares. 

 The ciliary processes, 

 about seventy in number, 

 form a circle of radial 

 , thickenings, each of a 



Meridional fibres of 



ciliary muscle somewhat triangular 

 shape ; the base of the 

 triangle is directed for- 



Pars ciliaris retinse Wards, towards the 



equator of the lens, while 

 the apex is continuous 

 behind with some three 

 or four ridges of the or- 

 biculus ciliaris. They 

 vary in size, the largest 

 having a length of 2-5 



Zonula ciliaris 



mm. 



The structure of the 

 orbiculus ciliaris and 

 ciliary processes is similar 

 to that of the chorioid, 

 but the capillaries are 

 larger and more tortuous, 

 and there is no lamina 

 choriocapillaris. The 



FIG. 683. SECTION THROUGH CILIARY REGION OF THE BULB OF THE EYE. deep surface of the ciliary 



processes is covered by 



two strata of columnar epithelium, the anterior layer of which is pigmented ; these 

 two strata form a direct continuation forwards of the retina and constitute the 



Cornea 



Anterior chamber 



Sinus venosus 

 sclerse 



Spatia angul 

 iridis 



Conjunctiva 



Pars iridica retinae 



Ciliary process 

 Ligamentum 

 pectinatum iridis 

 .Circular fibres 

 of ciliary muscle 



Sclera 



Perichorioidal lymph space 



Orbiculus 

 ciliaris 



Retina 



