134 WILLIAM HARVEY 



in these veins has the same colour and consistency as 

 in other veins, in opposition to what many believe to be 

 the fact. Nor indeed can we imagine two contrary mo- 

 tions in any capillary system the chyle upwards, the blood 

 downwards. This could scarcely take place, and must be 

 held as altogether improbable. But is not the thing rather 

 arranged as it is by the consummate providence of nature? 

 For were the chyle mingled with the blood, the crude with 

 the digested, in equal proportions, the result would not be 

 concoction, transmutation, and sanguification, but rather, 

 and because they are severally active and passive, a mix- 

 ture or combination, 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 con- 

 trary; 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 dis- 

 tinct, 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 

 portion of chyle or incompletely digested matter mingled 

 with the blood, nature has interposed the liver, in whose 

 meandering channels it suffers delay and undergoes ad- 

 ditional 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 an 

 anastomosis existing from the vena portae. The blood re- 

 turns from the intestines of the foetus, 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 foetus, even the genital 



