Of the Circulation cf the Blood. 13 
to I, out of H I arifcs a veinous fpring, delineated in K 
F L,; the blood moving from K to F, joins the other at 
F; and by this means, part of the blood coming from 
the artery, is thrown into the vein, as paffing from F 
to G, and to the belt of Mr. Leeuwenhoek’s obfervation, 
a quantity of blood, juft equal to that carried from K 
F to G, moves from C E to F, and directs its courfe 
upwards from F to L, fo that whatever quantity of an- 
terious blood paftes through K F and F G, an equal 
quantity of veinous blood returns through C E and F L. 
Though the agreeable motion of the blood was formerly 
apparent, yet this experiment afforded him a very clear 
perception of the above-mention’d variety ; and befides, 
this union of the blood-veffels was not formerly dii— 
cbver’d. 
Mr. Leeuwenhoek, in his 112th epift. has given us 
an accurate delineation of the blood-veffels in part of the 
tail of an eel, whofe whole length did not exceed that of 
the length of his little finger. The figure, as by him 
delineated, is reprefented in fig. 45. whereof ACE 
reprefents the veins, and B D F arteries. 
The letter D reprefents an artery, from which a 
branch G proceeds, that is divided about H, into two 
leffer branches, one of them reprefented by the letters 
H I K ; fo much of this fmall veffel as reaches to I, is 
called an artery, becaufe the blood may to that place be 
propelled in its progreffion from the heart. The other 
part I K of the fame branch may be called a vein, be¬ 
caufe by it the blood is convey’d hack again to the heart. 
In the other part of the fame branch H L M, the blood 
is drove forwards till it arrives at M, where it is dif- 
charged into the vein E, which in this figure is the firft 
place that can take the name of a vein. 
Here 
