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may obl'erve, that provident Nature, if not in all, at leaft in many 

 things which come under our hiveftigation, performs her operations 

 with the greateft uniformity ; for, in like manner, the cryftalline hu- 

 mour of the eyes, not only of men, but of the larger terreftrial ani- 

 mals, and alfo of fiflies, as far as I have examined into them, con- 

 fifts of a kind of fcaly parts, laid one on another : fo likev/ife the tu- 

 nica comea or horiiy coat of tlie eye, which coat, I at firfi: conceived 

 to be compofed of only three diftin6l menibrancs, but afterwards, on 

 a more accurate invefligation, 1 found to confift of an hundred 

 membranes, laid one on another like fcales. And I conclude that 

 this formation is defigned, not only to give the coats of the eye a 

 great degree of ftrength and firmnefs, but alfo, that if one of the 

 membranes fhould be hurt, the others may el'cape uninjured. 



It is the opinion of many, that the hairs on the bodies of men and 

 animals, are hollow, and fome think, that they contain in them a 

 marrow like tlie bones ; but thefe opinions are erroneous. Hairs 

 are formed with a kind of coat, which is analogous to tlie bark 

 of trees, and their internal fubllaiice confifts of ftreaks or fibres. 

 Their growth, is not like that of plants, but is produced by a 

 kind of propulfion, that is to fay, that the part which one day 

 is within the Vtun, and is as it were, the root, in a day or two, 

 is thruft out beyond the Ikin : and as, when the hair firfl comes forth, 

 it is, in all its parts, very moift, as foon as the moiflure begins to 

 evaporate, the coat or bark of the hair, and the fibres adjacent to it, 

 acquire a degree of firmnefs which prevents the hair from contra6iing 

 inwards, whence it comes to pafs, that, as the internal fibres continue 

 to dry, and thereby become thinner, they are divided afunder, and 

 recede from each other, fometimes forming one, and fometimes 

 more chinks, exhibiting a kind of darkifli furrow or furrows, v>hicli. 



