440 THE CIRCULATION OF THE BLOOD 



but, so far as the facts are concerned, they were the same for 

 him as for us. Well then, the first thing that Galen did was 

 to make out experimentally that, during life, the arteries 

 are not full of air, but that they are full of blood. And he 

 describes a great variety of experiments which he made upon 

 living animals with the view of proving this point, which 

 he did prove effectually and for all time ; and that you will 

 observe was the only way of settling the matter. Further- 

 more, he demonstrated that the cavities of the left side of 

 the heart what we now call the left auricle and the left 

 ventricle are, like the arteries, full of blood during life, 

 and that that blood was of the scarlet kind arterialised, 

 or as he called it " pneumatised," blood. It was known 

 before, that the pulmonary artery, the right ventricle, and 

 the veins, contain the darker kind of blood, which was thence 

 called venous. Having proved that the whole of the left 

 side of the heart, during life, is full of scarlet arterial blood, 

 Galen's next point was to inquire into the mode of communi- 

 cation between the arteries and veins. It was known before 

 his time that both arteries and veins branched out. Galen 

 maintained, though he could not prove the fact, that the 

 ultimate branches of the arteries and veins communicated 

 together somehow or other, by what he called anastomoses, 

 and that these anastomoses existed not only in the body in 

 general but also in the lungs. In the next place, Galen 

 maintained that all the veins of the body arise from the liver; 

 that they draw the blood thence and distribute it over the 

 body. People laugh at that notion now-a-days ; but if any- 

 body will look at the facts he will see that it is a very probable 

 supposition. There is a great vein (hepatic vein Fig. 1) 

 which rises out of the liver, and that vein goes straight into 

 the vena cava (Fig. 1) which passes to the heart, being there 

 joined by the other veins of the body. The liver itself is 

 fed by a very large vein (portal vein Fig. 1), which comes 

 from the alimentary canal. The way the ancients looked at 

 this matter was, that the food, after being received into the 

 alimentary canal, was then taken up by the branches of this 

 great vein, which are called the vena portse, just as the roots 

 of a plant suck up nourishment from the soil in which it 

 lives ; that then it was carried to the liver, there to be what 

 was called " concocted," which was their phrase for its con- 

 version into substances more fitted for nutrition than pre- 

 viously existed in it. They then supposed that the next 

 thing to be done was to distribute this fluid through the 



