05 . PHILOSOPHICAL TRANSACTIONS. [aNNO 1684. 



fore first examined the film or membrane which encloses it, and separates it 

 from the other humours of the eye; and conceived that it was constituted of 

 threads; but at other times, though great diligence was used, I could observe 

 none at all. 



In these inquiries, I have sometimes seen the impressions of the thread like 

 substance of the outermost scales of the crystalline humour, in the foremen- 

 tioned membrane ; whence I concluded, that one use of it might be, to fill up 

 all the unevennesses caused by the threads in the superficies of the crystal, and 

 so to constitute a perfect round. Another use of it may be, by compressing 

 the crystalline humour to alter its figure, and make it part of a greater or less 

 circle : and hence it may not improperly be called a muscle. 



Although it did not plainly appear that the film is constituted of threads 

 woven together, I make but little doubt of it ; because formerly, in the thinnest 

 membranes I have seen these thread-like appearances; and also having examined 

 the parts thereabout, I found a great many streaks or lines, seeming to be 

 lymphatic vessels, designed for the nourishment of the humours of the eye ; ~ 

 these I traced till they entered into the coat of the crystalline humour, and 

 then they grew so small that I lost sight of them. 



I further observed that the crystalline body was compounded of thin scales 

 placed upon one another. These seemed about 2000 thick ; for the axis, where 

 it was longest, was ^ of an inch, so that the distance from the centre to the 

 circumference is as ^ of an inch : now the length of an inch being 600 hairs 

 breadth, 4- must be 200 hairs breadth, which being multiplied by 10, the num- 

 ber of scales in the breadth of a hair, make 2000 scales, the thickness of this 

 crystalline body. I have further observed, that each of these scales is consti- 

 tuted of threads, which in a very neat order lie by one another, so that each 

 of these scales is the thickness of one of the threads. When we view the 

 crystalline body with attention, as it comes fresh out of the eye, we find it 

 excel in transparency the purest glass, though it is composed of so many thou- 

 sand threads, and that they lie very close together, so that it might justly be 

 wondered how the light can pass through them in right lines, which is abso- 

 lutely necessary ; for were it otherwise, the crystalline body would appear white, 

 and not transparent. To amuse some curious persons, and to represent the 

 crystalline body, yet plainer to their sight, I have taken a small tennis ball, 

 and wound the same about with a very fine cord, having before stuck in many 

 small pins, in the places where it was to be kept from slipping ; then I smeered 

 the ball over with strong glue, and when it was well dried, took out all the 

 pins, and then the ball with the cord wound about it, represents the crystalline 

 body of the eye. 



