One of Galen's medical breakthroughs was proving arteries carried blood & not this, as was believed
[DOC] [TLE] Galen - Wikipedia [PAR] Aelius Galenus or Claudius Galenus often Anglicized as Galen and better known 
as Galen of ... Galen's understanding of anatomy and medicine was principally 
influenced ..... Galen believed the circulatory system to consist of two separate 
one-way ...