( lit ) 



them aflvimes a difltrent figure, fo as to lie together and adjoin aS 

 ciofely as can be imagined. This my computation of the flefliy 

 Fibres (as they are denominated by a certain medical gentleman in 

 this country), I have here fet down in order to fhew their minute- 

 nefs, and the rather as the fame medical gentleman fuppofes, that 

 thefe flethy Fibres are inferted into the orifices of the veins and 

 end in the arteries, and that the circulation of the blood is performed 

 in thelc flefliy Fibres, and he fays that he has feen valves in them ; 

 but thefe his obfervations a§2 not taken from the microfcDpe, but 

 from tlie judgment of his naked eye, fo that, doubtlefs, he miftook 

 an entire flefliy mufcle for a fiefliy Fibre. 



Plate XV. Fig. l , is a flefliy Fibre, in which I have often ob- 

 ferv^ed fome foldings or inequalities, like wrinkles, as A B CD, and 

 others lying near them, as at E F G H, and again as at I K LM, and 

 in this manner, viewed by a common microfcope, they had the ap- 

 pearance of being compofed of globules; but a flefliy Fibre alio 

 appeared as at NOP Q, and this la ll appearance, I think, reprefents 

 truly the internal original filaments of which a flefliy Fibre is com- 

 pofed. 



Upon feeing this, I was able to fatisfy myfelf as to the reafon 

 why our fingers, arms, legs, and our whole bodies, while at reft, 

 do not lie in a right line, but fomewhat bent, and, as it were, tend- 

 ing to the pofition they were placed in before we were born ; and, 

 moreover, I think I can aflign the reafons of the motions of our 

 limbs, or rather the extenfions and contracflions of our mufcles, 

 namely, that when a mufcle is extended the flefliy Fibres compofing 

 it have no wrinkles or folds, but when a mufcle is not extended, 

 but contracted or thicker in figure, then each flefliy Fibre is full of 

 w^rinkies or i'olds. 



Fig. 2, ABCDEFGII is a flefliy Fibre which, by expanding 

 and comprefling it, in order more plahily to difcover the number of 

 filaments of which fo fmall a Fibre confifls, I caufed to open very 

 much in its component filaments, and it gave the reprefentation of 



