Page:The Harveian oration for 1874.djvu/45

 fifty years was needed to render Harvey’s great discovery possible. This is not to be forgotten by any of us labouring at mere details of which, when we have ascertained them most certainly, we yet cannot see the purport or the uses. Sooner or later they will surely find their place.

It would take too long to enumerate all the anatomical discoveries that were made during the fifty years before the time of Harvey. I will therefore mention those only which have reference to the circulatory system. During this time the relations of the vena cava to the heart on the one hand and to the portal vein on the other were ascertained. The existence and distribution of the valves of the veins were made out and their purpose was conjectured, though these conjectures were to a great degree erroneous. The tricuspid valve of the heart was described and its uses were correctly explained. The absence of any direct communication between the two sides of the heart was placed beyond reasonable doubt; and a theory