-, THE IRIS. 



supra-choroidea, or lamina fusea, which surrounds the large lymphatic space lined with 

 fZotlulhrni and called the perichoroidal space, q. In new-born infants, which according to 



Aristo^ the uveal tisSUe is deVOid f pigineUt; m brUDetteS {t iS 



developed later, and in blondes not at all. 



In X ciliary part of the choroid, the pigmented connective-tissue corpuscles are not so 

 ni,ni,.roiis' The ciliary muscle (tensor choroidese, or muscle of accommodation) is placed in 



hi" rerion It arises (), by means of a branched, reticulated, connective-tissue origin, from 

 the inm-r side of the junction of the cornea and sclerotic, near the canal of Schlemm, and 

 SS backwards to be inserted into the choroid. This constitutes the radiating fibres. 



,t 1, . fibres lying internal to these are arranged circularly t m bundles m the ciliary margin 

 These circular fibres are sometimes called Heinrich Miiller's muscle The muscle consists of 

 smooth muscular fibres, and is supplied by the oculomotonus ( 34o, 3). 



The iris consists of the following parts from before backwards :-a layer of epithelial cells (v) 

 continuous with those covering the posterior surface of the cornea, a layer of reticulated 





Fig. 516. Fig. 517. 



Fig. 516. Nerve-plexus in the cornea after gold chloride, n, nerve; a, fibrils. Fig. 517. Ver- 

 tical section of the choroid and a part of the sclerotic. (1) sclerotic ; (2) lamina supra- 

 choroidea ; (3) layer of large vessels ; (4) limiting layer ; (5) chorio-capillaris ; (6) hyaline 

 membrane ; (7) pigment epithelium ; (g) large blood-vessels ; (p) pigment-cells ; (c) sections 

 of capillaries. 



connective-tissue, the layer of blood-vessels, and lastly a posterior limiting membrane, which 

 contains the pigmentary epithelium (x) (Michel). In brunettes, the texture of the iris contains 

 pigmented connective-tissue corpuscles. The iris in some animals is described as containing 

 two muscles composed of smooth muscular fibres one set constituting the sphincter pupillse 

 (circular fig. 533), which surrounds the pupil, and lies nearer the posterior than the anterior 

 surface of the iris ( 392). Its nerve of supply is derived from the oculomotorius ( 345, 2). 

 The other fibres constitute the dilator pupillee (radiating), which consists of a thinner layer of 

 fibres arranged in a radiate manner. Some of the fibres reach to the margin of the pupil, 

 while others beud into the sphincter. [The existence of a dilator pupillse in man is denied 

 ( 392).] At the outer margin of the iris, the radial bundles are arranged in anastomosing 

 arches, and form a circular muscular layer (MerTcel). The chief nerve of supply lor the dilator 

 fibres is the sympathetic ( 347, 3). Ganglia occur in the ciliary nerves in the choroid, [and 

 they are found also in the iris]. Gerlach has recently applied the term ligamentum annulare 

 bulbi to that complex fibrous arrangement which surrounds the iris, and at the same time forms 

 the point of union of the ciliary body, iris, ciliary muscle, sinus venosus iridis, and the line of 

 junction of the cornea and sclerotic. 



The choroidal vessels are of great importance in connection with the nutrition of the eye. 

 According to Leber, they are arranged as follows : The arteries are 1. The short posterior 

 ciliary, which are about twenty in number and perforate the sclerotic near the optic nerve 



