Foli 't antes existing in the Aqueous Humour of the Eye. 167 



detached, arranged in lines, or mingled irregularly together. 

 The insulated specks exhibit a bright spot in the centre, 

 (I have sometimes however seen it dark,) surrounded by a 

 dark circle. They are, in fact, small lenses capable of con- 

 verging the rays which fall upon them to a minute focal point; 

 and the dark ring surrounding the central point is the sha- 

 dow of the circumference of the globule, from which the rays 

 of light have been directed to pass through the centre. In a 

 very bright light, no less than four dark circles may be seen, 

 the outer narrower and better defined than the inner ones. In 

 the lines or strings of globules, the dark shadow is also seen, but 

 under a different form, a double line of shade passing along 

 each side of the chain ; these lines appear to be indented at 

 intervals, but not very clearly, as if the globules had been 

 compressed by adhering to each other. On the slightest 

 movement of the eye-ball they change their position, and are 

 frequently lost sight of, but without any uniformity of direc- 

 tion or motion. The lines and groups, as well as the insulated 

 globules, are perfectly unconnected one with another. 



A close inspection in a good light discovers the minuter 

 globules in great abundance; their density is so trifling as merely 

 to give a spotted or mottled appearance to the fluid ; they move 

 altogether as if they formed a connected stratum, and in my 

 own case are interspersed with a few larger and brighter points 

 which keep their relative position. They will not sink much 

 below the centre of the eye, though they may be projected 

 above it; their descent is much slower than the motes de- 

 scribed above. But that they really do descend may be proved 

 by fixing the eye steadily, when they pass slowly downwards 

 across the centre of vision, most clearly; a sufficient proof that 

 they are not diseased points of the retina. It may perhaps be 

 said that they are merely the appearances which are produced 

 by the mucus and tears spreading over the cornea, brought 

 into view by the mode of examination mentioned above; but 

 their characters and position are not altered by winking, which 

 must happen if their source is external. In fact, the minute 

 divisions of mucus are sometimes seen; and, besides the cir- 

 cumstance of their instant removal by winking, they differ so 

 much from the internal globules as to be immediately distin- 

 guished from them. 



What part of the eye, then, can be considered as the seat of 

 muscae, possessed of the characters ascribed to these, parti- 

 cularly their great and irregular mobility, if not the aqueous 

 humour ? 



XXX. On 



