22 Of the Circulation of the Blood < 
. Fig. 48. M, L, R, S, reprefents a microfcopic pi&ure 
of a part of the frog’s gut, and mefentery extended, by 
means of the fifti hooks R, S, M, the ends of their firings 
being pegged to the fquare frame, one of which is feen 
at p. B, I, K, C, is a part of the body of the frog. 
And I, K, that part where the belly was opened. D, E, 
part of the fquare brafs frame. The {haded part within 
the gut, marked M, L, R, S, is called the mefentery, in 
which is plainly feen the blood-veffels. Thofe vefiels, 
which are a little darker than the reft, are called arteries. 
In every one of which I plainly faw a pulfe, and the blood 
{lowing from A to R. The others are veins, through 
which the blood flowed in a conftant ftream, in the 
diredHon V, N. 
As there are many fmall filh, whofe fins are more 
tranfparent than their tails j I thought it might be ac¬ 
ceptable in this place, to give a cut of the manner how 
they may be fattened upon the fame frame the frog was, 
which take as follows. 
Firft cut a piece of leather in the fhape of fig. 49. and 
tie a firing to each corner of it, as at A, B, C, D, and 
obferve, that the part G H of the leather be no longer 
than from the fiih’s neck to the part where the tail begms 
to grow fmall, and cut a flit'.from A to I, and from B to 
K,- then put the firing C E through the flit A I, and the 
firing D F through the flit B K, and put the fifil in head 
foremoft; after which draw the firings clofe, and apply 
it to the frame, fig. 50. fixing down the firing D F to 
the frame by the peg N, and the firing B M by the peg 
O. The firing C E may be made fall with the peg P, 
and the firing A L with the peg Q, in which pofition 
the fifil cannot poflibly get away, but on the contrary 
will lie exceeding quiet: then may you ftick a fifli-hook 
to the thick part of its fin at R, and ftretch it out by 
drawing 
