94 THE ENGINES OF THE HUMAN BODY 



But how did the blood reach the left chamber of the 

 heart ? When it reached that chamber there was no 

 doubt concerning what happened to it ; it became mixed 

 with air, and in the mixing vital spirits and heat were 

 generated. There was indeed a difficulty as to how the 

 blood found its way to the left ventricle. We have seen 

 that blood, according to Fabricius, was concocted in the 

 liver and distributed by veins to the body. We also 

 observed that the upper caval vein had a wide opening 

 into the right auricle of the heart. Indeed, it seems to 

 pass through and form part of the right auricle (fig. 25). 

 From the right auricular chamber blood entered the right 

 ventricle, and from there passed along a great channel — 

 the pulmonary artery (fig. 26) — to enter and nourish the 

 lungs. The difficulty came when Fabricius had to explain 

 how the blood found its way from the right ventricle 

 into that great brew chamber — the left ventricle. 

 Between them there is a thick muscular wall or 

 septum, with never a pore or opening to be seen in 

 it. "That," said Fabricius, "was just as it should be" ; 

 visible holes were not necessary ; sweat exuded from 

 invisible pores of the skin, and it was by a process of 

 sweating that blood passed from the right to the left 

 ventricle. 



Thus, having shown how air and blood reach the left 

 ventricle, Fabricius proceeded to show how the hot 

 vitalised blood thus formed was made to ebb and flow 

 throughout the body. One had only to place a finger on 

 the artery of the wrist to know that arteries expanded or 

 went into a state of diastole, and then contracted or went 

 into a state of systole seventy to eighty times a minute. 

 They were expanding pumps which sucked the vitalised 

 blood into the tissues of the body and then contracted 

 and forced the blood backwards to the centre of the body 

 again. It so happens, as we now know, that when the 

 heart contracts its apex, resting against the front wall of 

 the chest, can be felt to press forwards as if it were then 

 expanding or in a state of diastole — as indeed Fabricius 

 thought it was. He therefore had no difficulty in con- 



