ORGANS OF THE SENSES. 511 



namely, by vertical and horizontal sections, and by the use of 

 re-agents, but to no purpose. 



In a representation of a vertical section of the human 

 cornea given in the te Physiological Anatomy," this anterior 

 elastic lamina is represented as being three or four times the 

 thickness of the posterior lamina, so that there ought to be 

 but little difficulty in its detection were it present on the 

 face of the human cornea. 



The " elastic cords " mentioned would appear to be nothing 

 more than the nucleated fibres already described as passing 

 in a curved manner from the surface of the cornea, and 

 extending deeply into its substance. (See Plate LXVII. 

 fig.l.) 



Choroid. 



The next membrane met with in the usual order of dissec- 

 tion, is the choroid : this adheres intimately to the schlerotic 

 in the neighbourhood of the larger trunks of the venae vor- 

 ticosae ; but more slightly in the intervals between, being 

 united to it only by the lamina fusca. 



The choroid forms a thick membrane, externally of a 

 chocolate colour, flocculent and rough, but internally of a 

 bluish-black colour and smooth; its substance is made up 

 of numerous blood-vessels, and of an immense quantity of 

 pigment in connection with a peculiar form of fibrous tissue. 



The tissue of which the choroid is composed, has been 

 hitherto stated to resemble the fibrous tissue of the schlerotic : 

 this is not the case, however, as indeed might have been in- 

 ferred from the ease with which it tears, especially in the 

 course of the vessels, and the absence of bundles of fibres on 

 the torn and divided margins : the fibrous element of the 

 choroid is of a peculiar kind, to be more fully described here- 

 after, and unlike any other form existing in the human body. 



The blood-vessels of the choroid are usually described as 

 forming two layers, and this they may be fairly considered 

 as doing, although the two lamellae are not perfectly distinct 

 from each other, being connected by numerous blood-vessels 

 which pass between them. 



s s 3 



