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I thinlc no fountain whatfoever, either natural or artificial, or indeed 

 any other fpedlacle, could have afforded me fuch plealure as thele 

 fniall animals. 



Fig. 24, repreferrts a Tadpole, when grown to fuch a fize that 

 both its hind feet were formed, and it could ufe them; the two fore 

 feet were alfo vifible, but as yet lay hid under the Ikin. 



jSIoreover, I examined the Tadpoles when they were fo far per- 

 fected as to become Frogs and leap about the fields, and in thefe I 

 alfo difcovered a great number of wonderfully minute blood- vellels, 

 which with their bendings conllituted thofe vellels we call arteries 

 and veins; fo that it moft manifeilly appeared to me that the 

 arteries and veins are only a prolongation of one and the fiime 

 veliel. And this was moll; particularly manifelt in the extremity 

 of thofe parts in the foot, which may be called the fingers, and of 

 which the Frog has four in each of the fore feet and five in the 

 hind feet. 



Thefe blood veflels, which we call veins and arteries (though in 

 fact they are one and the fame), were to be feen in great numbers 

 at the extremities of thofe fingers, and each of them had a round 

 bending, fo that the dillincl courfe of each of them could not indi- 

 vidually be difcovered. All thefe veflels were fo fmall and thin that 

 they only admitted the paflage of the blood in fingle globules. But 

 when I examined them at the firll or fecond joint of the fingers, 

 then I faw the arteries and veins were larger, fo that the blood in 

 them was of a red colour. 



I did not only examine thefe young Frogs in parts of their bodies 

 only, but placed their whole bodies before the microfcope, and the 

 before mentioned blood-velfels appeared to me as I have already de- 

 fcribcd them. This circulation I fhewed to two refpedable gen- 

 tlemen, who could not behold the fight without great admiration, 

 efpecially in thofe places where they faw the blood running in fuch 

 fmall vellels as to be only pervious to one of thofe particles, \^•hence 

 its rednefs proceeds. 



Vol. II. G g 



