i] His Forerunners and Followers. 21 



and every action and process of the body, has for its fundamental 

 basis the fact that the life of every tissue unit of the body is 

 dependent on that unit being bathed directly or indirectly by 

 blood which comes to it as oxygen-bearing, arterial blood, and 

 leaves it as venous blood carrying away the products of activity. 

 Let us remember that such a view is impossible under the 

 Galenic doctrine which taught that to and from every tissue 

 there was a flow and ebb of two kinds of blood, serving two 

 purposes, one kind travelling in the veins, the other in the 

 arteries. Let us further remember that this Galenic doctrine 

 of the uses of veins and arteries was bound up with the Galenic 

 doctrine of the working of the heart. If we do this we shall 

 at once see that the true teaching of the mechanism of the 

 bodily heart is as it were the intellectual heart of all phy- 

 siology, and understand how Harvey in overthrowing the 

 Galenic doctrine of the action of the heart, overthrew much 

 more than that, and cleared the way for true conceptions of the 

 actions of all parts of the body. 



The central idea of the Galenic doctrine was the mysterious 

 transit of blood from the right to the left side of the heart 

 through the invisible pores of the septum. The transit which 

 Galen supposed to take place was not a complete transit of the 

 whole contents of the right ventricle, such as we now know is 

 effected through the pulmonary circuit, but only a transit of 

 some of the contents, the rest flowed and ebbed along the 

 veins, just as the contents of the left ventricle flowed and ebbed 

 along the arteries. But such a partial transit furnished the 

 whole intercourse between the right side and the left ; and all 

 the conceptions of Galen as to what took place in the lungs, in 

 the arteries, in the veins, and in the heart itself were dependent 

 on the occurrence of this passage of blood through the appa- 

 rently solid septum. 



We have seen that it was just this part of the Galenic 

 doctrine which excited Vesalius' strongest doubts and his most 

 pronounced sarcasm. It was attacked also by others ; some of 

 these were Vesalius' pupils, direct or indirect, but one was not. 



In Spain, in the land where above all other places the 

 Church and the Inquisition were stifling inquiry, in Villanueva 



