442 THE CIRCULATION OF THE BLOOD 



we now-a-days use, for the word pneuma. Then he 

 imagined that the blood, further concocted or altered 

 by contact with the pneuma, passed to a certain extent 

 to the left side of the heart. So that Galen believed 

 that there was such a thing as what is now called the pul- 

 monary circulation. He believed, as much as we do, that 

 the blood passed through the right side of the heart, through 

 the artery which goes to the lungs, through the lungs them- 

 selves, and back by what we call the pulmonary veins to 

 the left side of the heart. But he thought it was only a very 

 small portion of the blood which passes to the right side of 

 the heart in this way ; the rest of the blood, he thought, 

 passed through the partition which separates the two ven- 

 tricles of the heart. He describes a number of small pits, 

 which really exist there, as holes, and he supposed that the 

 greater part of the blood passed through these holes from 

 the right to the left ventricle (Fig. 2). 



It is of great importance you should clearly understand 

 these teachings of Galen, because, as I said just now, they 

 sum up all that anybody knew until the revival of learning ; 

 and they come to this that the blood having passed from 

 the stomach and intestines through the liver, and having 

 entered the great veins, was by them distributed to every 

 part of the body ; that part of the blood, thus distributed, 

 entered the arterial system by the anastomoses, as Galen called 

 them, in the lungs ; that a very small portion of it entered 

 the arteries by the anastomoses in the body generally ; but 

 that the greater part of it passed through the septum of the 

 heart, and so entered the left side and mingled with the 

 pneumatised blood, which had been subjected to the air 

 in the lungs, and was then distributed by the arteries, and 

 eventually mixed with the cifrrcnts of blood, coming the 

 other way, through the veins. 



Yet one other point about the views of Galen. He thought 

 that both the contractions and dilatations of the heart 

 what we call the systole or contraction of the heart, and the 

 diastole or dilatation Galen thought that these were both 

 active movements ; that the heart actively dilated, so that 

 it had a sort of sucking power upon the fluids which had 

 access to it. And again, with respect to the movements of 

 the pulse, which anybody can feel at the wrist and elsewhere, 

 Galen was of opinion that the walls of the arteries partook 

 of that which he supposed to be the nature of the walls of the 

 heart, and that they had the power of alternately actively 



