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cylindrical nucleus with some granular pigment. How far it 

 extends outwards, and whether the circular fibres reach the 

 periphery of the iris, a? in reptiles, I am unable to say. 

 Radial bundles of spindle-cells, resembling those of the 

 sphincter are also certainly present. 



The Coats of the Eyeball. 



Conjunctiva. — The conjunctiva is a thin membraniform webof 

 areolar tissue with an external epithelium. The structure of 

 the palpebral part differs slightly from that of the ocular. The 

 former is a tougher, the latter a looser texture. The palpe- 

 bral part is beset with simple vascular papillae. The epithe- 

 lium consists of several layers of cells, the deepest of which 

 are oblong, and stand vertically ; while the more superficial 

 are flattened, and obliquely packed. The meshes of the 

 areolar tissue often enclose large numbers of lymph-like 

 corpuscles. The blood-vessels and nerves are numerous. 

 The nerves are remarkable for the specialized terminations 

 some of the tubules exhibit, the terminal clubs (end kolben), 

 named after their discoverer Krause. 



The loose fold of conjunctiva which connects the lid and 

 globe and also the palpebral part, but more particularly the 

 former, contains small glandiform bodies — minute spherical 

 capsules, enclosed in a net of minute capillary blood- 

 vessels, and, according to some observers, also surrounded 

 by lymphatics. These, when enlarged, form the transparent 

 bead-like grains which characterize a kind of granular 

 ophthalmia, fortunately for us much less frequent in Great 

 Britain than the pupillar form of this complaint. 



Sclerotic. — The sclerotic, in conjunction with the cornea, 

 forms the strong case of the eyeball which supports and pro- 

 tects the delicate inner coats. It is thickest behind, around the 

 optic nerve ; becomes thinner from here to the attachment of 

 the tendons of the musculi recti, in front of which its thick- 

 ness again slightly increases. A funnel-shaped canal pierces 

 it behind for the passage of the optic nerve, and it is per- 

 forated by many smaller apertures for the transmission of 

 blood-vessels and of the ciliary nerves. Of these inner 

 openings the only ones which require notice are those by 

 Avhich the venge vorticoste choroidese leave the eyeball. These 

 pierce the sclerotic obliquely, which renders them valvular, 

 a mechanism which lessens the available opening whenever 

 the pressure on the inner surface of the sclerotic rises unduly, 

 and proportionately retards the egress of the venous blood, 

 and raises the pressure still higher. 



The sclerotic is principally composed of white fibrous or 



