SENSITIVE SYSTEM. 389 



angle of inflection presents to minute inspection (or through a 

 magnifying glass) numerous delicate and faintly-marked stripes, 

 arranged in parallel radii, which are the cilianj strice ; and every 

 two or more of these striee unite afterwards to form a single 

 plait or ciliary process, that runs direct to the crystalline lens, 

 growing broader as it proceeds, adhering in its way to the raem- 

 branula ciliaris (which is behind it), and terminating with an 

 angular point at the capsule of the lens, with which, though in 

 contact, it has no connexion whatever. The best view we can 

 have of these processes is obtained by making a perpendicular 

 section of the eye and looking at them through the remaining 

 portion of vitreous humour: a broad, black, well-defined line 

 will then be seen, shewing their union with the choroides; and 

 in consequence of their posterior edges having a greyish cast, we 

 are enabled to distinguish their interstices filled with black 

 pigment. We can also distinguish that they vary in length, but 

 not perceptibly in breadth. 



The retina (so called from its supposed reticulated texture) 

 is the third or innermost tunic. The optic nerve, having reached 

 the inner and inferior part of the globe, pierces the sclerotic and 

 choroid coats, and in its passage through them grows somewhat 

 contracted in its diameter : having arrived at the internal part, 

 the nerve swells into a little, white, eminent papilla (appearing 

 as a white spot in the living eye), from whose circumference 

 issues, in white radiating lines, a medullary pulp which spreads 

 over the entire surface of the dark chamber. It is sustained in 

 this state of globular expansion by the vitreous humour, and 

 thus becomes accurately applied to the choroides externally, but 

 without contracting any adhesions whatever until it has reached 

 the corpus ciliare. In an eye perfectly recent, and unpre- 

 pared in any way for the examination, the retina appears to 

 terminate on a sudden, by a defined edge, at the black 

 circle upon the ciliary body, by adhesion there to the tunica 

 vitrea : it is asserted, however, by some anatomists, that it 

 does not end but only grows much thinner here, afterwards 

 extending almost imperceptibly between the ciliary processes and 

 tunica vitrea, and proceeding to the capsule of the lens ; and this 

 part, they say, in consequence of being much compressed, puts 

 on the appearance of nervous striae ; whereby, they add, its con- 

 nexion with the iris becomes established. During life, the re- 

 tina is transparent — the choroides shines through it and gives 

 colour to the pupil ; but speedily after death, it loses its pellu- 

 cidity, and exhibits a dead or opaque whiteness : immersion in 

 spirits of wine produces the opacity at once, at the same time 

 giving to the membrane a degree of firmness". — lit composition, 



