VOL. XIV.] PHILOSOPHICAL TRANSACTIONS. gS 



I also took out of the eyes of sheep, hogs, dogs, &c. the crystalline bodies, 

 and ordered them as I had done those of an ox ; and have found not the least 

 variation, either in the scaly parts, or in the course of the threads, composing 

 those scales. 



I have often endeavoured also to discover the nature of the vitreous humour 

 of the eye ; and which surrounds for the most part the crystalline humour ; as' 

 I imagined it was no watery matter, but rather a transparent muscle. But not- 

 withstanding all the means used, I could not make the least discovery thereof, 

 as this matter always changed into a watery substance. 



I further examined the crystalline body of the eyes of fishes, which are 

 perfect globes; and found them also constituted of like thin scales, lying one 

 over another, as in the former animals: and each scale also composed of 

 threads; but these threads run not in the same manner as those of other 

 animals; yet, notwithstanding all the industry used, I could never discover 

 their true course ; for when the threads approach the centre, they appear so 

 thin, and are so close joined together, that the sight cannot trace them; and 

 causing such a confusion, that I cannot be certain whether they end in the 

 centre, or return again from thence. 



I have also examined the crystalline bodies out of the eyes of birds, only to 

 view how the threads of the scales, constituting also the crystalline body, run ; 

 and after many observations, I have discerned that the threads constituting the 

 crystalline body of a turkey-cock, are extended like those in fish ; but as the 

 crystalline body of a fish's eye is perfectly globular ; those of birds are a fiattish 

 round towards the cornea tunica. And when from without the crystalline body 

 of the eye of a turkey-cock, I had with a very sharp knife taken off many of 

 the scaly parts, to bring it to a smaller globe, it changed its figure, and became 

 an oval ; the threads being, where they meet, so thin and small, that at last 

 they are not distinguishable. From whence we may conclude, that the threads 

 of the scales, which lie nearest the centre, are in the midst thin, and thus 

 make an oval figure : and that when the crystalline body increases in magnitude 

 the threads become then in the midst thicker ; and thus constitute a fiat round; 

 as I have perceived it for the threads in the crystalline body of a turkey-cock, 

 in their thickest part, were thicker than those in an ox, hog, sheep, &c. 



Before concluding, I cannot but mention, that I have by several ways and 

 means, seen with my naked eye, a thready substance, like that of the crystalline 

 humour. I shall only mention two of them, viz. I take a clean wine glass, 

 and hold the rim close against the pupil of one of my eyes, while the other 

 eye is closed; and looking thus firmly through the rim of the glass, against the 

 iiame of a candle, or other light, I perceive the thread-like appearance above- 



