92 Motion of the 



rather arranged as it is by the consummate providence 

 of nature? For were the chyle mingled with the blood, 

 the crude with the concocted, in equal proportions, the 

 result would not be concoction, transmutation, and 

 sanguification, but rather, and because they are 

 severally active and passive, a mixture or combina- 

 tion, or medium compound of the two, precisely as 

 happens when wine is mixed with water and syrup. 

 But when a very minute quantity of chyle is mingled 

 with a very large quantity of circulating blood, a 

 quantity of chyle that bears no kind of proportion to 

 the mass of blood, the effect is the same, as Aristotle 

 says, as when a drop of water is added to a cask of 

 wine, or the contrary ; the mass does not then present 

 itself as a mixture, but is still sensibly either wine or 

 water. So in the mesenteric veins of an animal we do 

 not find either chyme or chyle and blood, blended 

 together or distinct, but only blood, the same in colour, 

 consistency, and other sensible properties, as it appears 

 in the veins generally. Still as there is a certain though 

 small and inappreciable proportion of chyle or uncon- 

 cocted matter mingled with this blood, nature has inter- 

 posed the liver, in whose meandering channels it suffers 

 delay and undergoes additional change, lest -arriving 

 prematurely and crude at the heart, it should oppress 

 the vital principle. Hence in the embryo, there is 

 almost no use for the liver, but the umbilical vein 

 passes directly through, a foramen or anastomosis 

 existing from the vena portse, so that the blood 

 returns from the intestines of the fcetus, not through 

 the liver, but into the umbilical vein mentioned, and 

 flows at once into the heart, mingled with the natural 

 blood which is returning from the placenta ; whence 

 also it is that in the development of the foetus the liver 

 is one of the organs that is last formed; I have observed 

 all the members perfectly marked out in the human 

 fcetus, even the genital organs, whilst there was yet 

 scarcely any trace of the liver. And indeed at the 



