VOL. XXVI.] PHILOSOPHICAL TRANSACTIONS. 493 



the practice of physic ; where our skill in curing diseases, whose histories are 

 known, is always proportional to our knowledge of the animal economy, which 

 of itself is a considerable part of natural philosophy. And he affirms, that 

 every man who practises, does it on some knowledge of the animal economy,, 

 or some notions of his own, which are more or less clear, according to his skill 

 in natural philosophy. He proves likewise from Hippocrates and Galen, that the 

 principle of attraction of the small particles of matter to one another, was 

 known to the ancients ; the philosophy of Hippocrates being built on a certaia 

 propension which some things have to one another, by which they attract, 

 retain, and alter each other. 



In the first discourse, he proves by observation, that both the red and serous 

 parts of the blood are endowed with an attractive power ; and as in the blood 

 the particles attract one another, and cohere together, so likewise do the parti- 

 cles of different fluids, that are separated from it by secretion. He says, it is 

 evident that some of the fluids, that are secerned from the blood by the glands, 

 are really composed by the cohesion of several sorts of particles ; for in milk 

 there are 3 or 4 several sorts of substances ; urine has the same appearances, 

 and contains perhaps more principles ; and there is no doubt but that tears, 

 spittle, and sweat, are all compounded liquors. Now if the particles which 

 attract one another, be more powerfully attracted by the fluid in which they 

 swim, than by one another, they can never of themselves separate from the 

 fluid ; which is the case of salts dissolved in a large proportion of water, and of 

 urine when it rteither breaks nor settles : but if the particles swimming in the 

 fluid be more strongly attracted by one another than by the fluid, they must 

 necessarily separate from it, and go into parts which will either sink, swim, or 

 ascend in the fluid, according to their specific gravity. This power of attrac- 

 tion, he says, is universally diffused throughout all matter, and it seems to be 

 the only principle from which there can be drawn a satisfactory solution of the 

 phaenomena produced by the minima naturae. And because the whole animal 

 economy depends upon it, he lays down, in eleven propositions, so many of 

 the laws of that universal attraction, with their demonstrations, as are requisite 

 for his present purpose ; and then proceeds to show how the corpuscles, that 

 compose the secretions, are formed in the blood, before they arrive at their 

 secerning glands : but because the particles of the blood returning by the veins, 

 and attracting one another, are formed into globules too large for any secretion, 

 he shows how these globules are broken and divided in the lungs, by the force 

 of respiration : and from experiments, and the doctrine of statics, he calcu- 

 lates the pressure of the air on the lungs to be equal to the weight of lCX)lb; 

 and because the difference between the greatest and least gravity of the air is 



