[ 1 
IIL Part of a Letter /rd/^^- M Lewenhoek^ 
ceming the circuiafion mi globules, of the 
Blood in Butts. 
Delph in Holland, July 9. 1 700. 
During tfi^s Winter, I have ^ o^^ obferved the 
Boys* looking for ' fmall livihg Butts in the 
Smelts that are fold juft by my Houfe, in order to 
throw 'em into water, and entertain themfelves with 
beholding the uncommon motion of that little Fifti 
v/hen it fwims, as being different from that of all o- 
ther Fifties. 
This put it in my head to look more narrowly into 
thofe little Fifties, fome of which were fo fmall, tlfet 
the whole Body, bating the Tail, wa^no longer than 
an inQh. — - , 
Having'Often examined em with aMagnifying-glafs, 
in order to fee the circiJatibh bflthe Blood, (with 
which I am much delighted) and the variety of its 
motion, ru)t only f or my own fafisfa&i^ but that of 
feveral Learned Gentlemen, to whom I fihew'd the fame, 
my thoughts were again pointed upon thofe little par- 
ticles which entitle the Blood:' ta.its red colour, 
I formerly afferted to be flat and oval. 
The greateft motion of the Blood obfervable thro 
the Fins, was on each fide of the many little fingle 
Bones plac'd among the- Fins - vHiere the Blood vellels 
were fo large, that twenty five of the above-mention'd 
particles could pafs in a Breaft ^ but dwindled as they 
drew nearer to the extremity of the Fins, fmall Veflels 
being ail along detaclVd from the Arteries. 
Qfi one fide of a little Bone runs an Artery, and on 
the 
