subject which was not improved upon for fully 1,300 years. I have
endeavoured, in Fig. 2, to make clear to you exactly what it was he
tried to establish. You will observe that this diagram is practically
the same as that given in Fig. 1, only simplified. The same facts may
be looked upon by different people from different points of view. Galen
looked upon these facts from a very different point of view from that
which we ourselves occupy; 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. Furthermore, 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 communication
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