De venarum ostiolis.

Fabricius, teacher of Harvey at Padua, discovered the venous valves, and illustrated them in life-size copperplates in this monograph. He failed to recognize their true function, however, considering their function simply to delay blood flow. Fabricius's work must have influenced Harvey to direct his experimental efforts toward an accurate explanation of the function of the venous valves. This line of research eventually led Harvey to develop an accurate knowledge of how the circulation worked. Facsimile edition, with English translation, edited by K. J. Franklin, 1933. Digital facsimile of the 1603 edition from di.mospace.umsystem.edu at this link.