VOL. XXII.] PHILOSOPHICAL TRANSACTIONS. 493 



In pursuance of this new observation, I viewed the circulation of the blood 

 with glasses that magnified still more than any I have yet used ; by which at 

 last the oval figure of the particles was plainly made out. Now the greater the 

 magnifying glass is, the swifter does the circulation of the blood appear in the 

 vessels. Having retarded this motion, I employed two or three seconds of time 

 in observing the little veins ; and found that in several small vessels the oval 

 particles were so broke that I cooild neither see them nor those of which six had 

 made up a particle of blood ; but only a simple fluid of a Aiint colour running 

 along the vessels ; but in a large artery at the tail, the blood moved so slowly 

 that I could easily discern that the particles in that vessel were oval ; and not 

 only so, but I likewise perceived more clearly than before the little globes that 

 constitute the oval particles, if not always, at least for the most part. For it is 

 easy to conceive how fj little globules, which are pliant and always in motion, 

 and driven one upon another, should settle in the fashion of a bowl. Thus 

 fig. 9 represents the first coalition of the 6 little globules into one. I have 

 made up such a globe as is represented in the last figure of 6 wax balls put to- 

 gether, to show the form and composition of the little globular particles of the 

 blood; and I am certain each of these little globes is at least compounded of 36 

 others. These little bullets being moved and squeezed together, and being at 

 the same time pliant, and packed up into one complete round form, are repre- 

 sented fig. 10. 



From such a scheme we may conceive how the globular parts of the blood of 

 man and other animals acquire a roundness; but how the oval particles are com- 

 pounded of the 6 globules is not easy to apprehend. And should we divide one 

 of these globules by our imagination into smaller and smaller parts, the little 

 particles that enter into the composition will still be inconceivably smaller. Yet 

 supposing we could discover the figure and shape of parts less than a globule of 

 blood by a thousand millions, we should still be far from reaching the first con- 

 stituent parts. 



That venous blood may become arterious without being first in the heart, ap- 

 pears by the following experiment. Suppose ab in fig. 1 1, to be a vein, in which 

 the blood, seen through a magnifying-glass, passes with great celerity from b 

 to A. From this vein run two little branches, c and d, which unite between 

 E and F. Now supposing hi to be an artery in which the blood moves upwards 

 with equal swiftness from h to i. Out of hi arises a venous spring, delineated 

 in K, F, L. The blood moving from k to f joins the other in f ; and by this 

 means part of the blood coming from the artery is thrown into the vein, as 

 passing from f to g ; and to the best of my observation, a quantity of blood 

 just equal to that carried from kf to g, moves from ce to f, and directs its 



