38 HARVEY AND GALEN
He also had strange theories of the production of swelling and tension by the pneuma, which, of course, were totally erroneous 1 , and hence his theory seems more remote from modern science than it really is. But it might be shown, if I had time, how curiously he thought the presence of pneuma in the cerebral ventricles was proved by his numerous and careful experiments on the living brain. His method of investigation was in intention perfectly sound.
It is strange, too, that Galen was by no means absolutely wedded to the theory of a pneuma passing through the nerves. He says he has never been able to make up his mind whether the pneuma itself passes down into the nerves, or whether some kind of messenger descends from the brain so as to alter the constitution of the nerves, and this alteration is propagated to the parts which are moved. Again, some think, he says, that the action of the brain takes place by force ( btvafjus ) without matter, so that there is a flowing down of force from the brain ; in fact, the modern view. This distribution of force he supposes to be equivalent to the communication of an altered state, which seems to be the most modern view of all, that nervous ac- tion consists in a transmission of molecular change through the nerve. This he illustrates by a fine and suggestive comparison with the radiation 6f the stin, which passes through the air and alters it, though the sun remains in its own place. Between all these views, he says, we cannot decide offhand 2 .
The above extracts show how much a difference of language hinders us from understanding the thoughts of ancient writers ; and also, I think, demonstrates the essen- tially scientific basis of Galen’s mind, often concealed by his excessive subtlety and ingenuity.
Galen maintained the doctrine of the Hippocratic school, if not of Hippocrates himself, and of Plato, that the brain
1 To find still stranger performances ascribed to the 'spirits' we have only to look at the works of Willis, On the Brain, &c.
2. De Placitis, lib. vii. cap. 4; Kuhn, v. pp. 6ri, 617.
