XI EYE 183 



The interior of the globe (v.c) is filled with a colour- 

 less, transparent jelly, the vitreous humour, surrounding 

 which, everywhere but on its external face, is a thin 

 semi-transparent membrane, reddish when perfectly 

 fresh, but becoming grey soon after death ; this is the 

 retina (r). Between the retina and the sclerotic is a 

 vascular membrane called the choroid (did), the inner 

 face of which, i.e., that in contact with the retina, is 

 coloured black. It is this layer of black pigment which 

 gives the dark tint to the semi-transparent sclerotic in 

 the entire eye ; strictly speaking, it belongs to the retina, 

 but actually it adheres to. the choroid and appears like 

 the innermost layer of that coat. The retina is readily 

 detachable from the choroid, but at the place where the 

 optic nerve enters (blind spot, b. s) it becomes continuous 

 with the fibres of the latter, which pass through the 

 sclerotic and choroid. The choroid is made up of 

 connective-tissue and contains numerous vessels as 

 well as pigment-cells. 



Lying just internal to the pupil is a nearly globular 

 body, perfectly transparent when fresh, the crystalline 

 lens (I) \ it is kept in place by a delicate membrane, the 

 capsule of the lens. The iris, w r hich covers the outer 

 face oi the lens except \vhere it is perforated by the 

 pupil, is covered on its inner surface with black pigment, 

 and is continuous all round its outer margin with the 

 choroid. Between the iris and the cornea is a space, 

 the aqueous chamber of the eye (aq. c), which contains a 

 watery fluid, the aqueous humour. The main cavity of 

 the eyeball, containing the vitreous humour, is called 

 the vitreous chamber. 



The actual relations of these parts in the entire eye 

 are best grasped in a vertical section, such as is repre- 

 sented in Fig. 57. B. The main part of the eyeball forms 

 a chamber, enclosed by the sclerotic, darkened internally 



