HARVEY AND EXPERIMENTAL OBSERVATION 49 
ebb and flow. In reference to the anatomy of the blood- 
vessels, he goes so far as to say of the portal vein and the 
vena cava in the liver that ‘the extreme ramifications of these 
veins inosculate with each other, and in many places appear 
Fic. 11.—Scheme of the Portal Circulation According 
to Vesalius, 1543. 
to unite and be continuous.” All who followed him had the 
advantage of his drawings showing the parallel arrangement 
of arteries and veins, and their close approach to each other 
in their minute terminal twigs, but no one before Harvey 
4 
