GREECE AND SCIENCE AND MEDICINE 63
of Embryology, then Galen is the Father of Experimental Physiology. For he discovered that certain nerves were motor to certain muscles of the back, that the inferior laryngeal nerve was the nerve of voice, that the spinal cord was the conductor of impulses necessary for sensa- tion, and that those crossed from one side to the other in it. Galen recognized thirly pairs of spinal nerves and seven pairs of cranial; he knew of sensory fibers in the abdominal sympathetic, and of the vital importance of the medulla oblongata.
The Galenical doctrine of spirits — natural, animal, vital — domi- nated physiology for fourteen centuries. Galen corrects Aristotle in making the nerves proceed from the heart, but at the same time he denies that the heart has any nerves of its own. He still thinks that in breath- ing, air is drawn into the chest to cool the heat of the heart, but he recognizes that "sooty'* matter escapes from the lungs; he believes that the liver forms blood from digested food.
Galen knew tears to be the secretion of a gland and not an escape of aqueous humor: he discovered the six pairs of muscles of the eyes, and the muscles of the larynx. It was he who first described the Tendo Achillis, which quite explains why it has a Greek name. Galen's view of structure was always physiological, hence the titles of his works —
- ' De nsu partium corporis himiani, " De motu musculorum, " De mor-
borum causis." It was on the vascular system that Galen had least light. No notion of a circulation occurred to him. He thought that blood conveyed by the veins to the tissues was there used up in nourish- ing them. Crude blood with animal spirits from the liver, he thought, passed to the heart where the vital spirits were originated; animal spirits being produced as a further result of a refining process when the arterial blood had reached the brain. "Spirits" are too firmly em- bedded in our language for us ever to get rid of them. Galen imagined that the blood of the great pulmonary artery went to nourish the sub- stance of the lungs, a notion of which Harvey pointed out the inherent improbability. Galen did, however, discover that an artery has three coats. He insisted that blood passed from the right to the left side of the heart through pores in the septum: Vesalius ridiculed this asser- tion, Harvey disproved it.
Galen r^arded the heart as the seat of courage and the liver of love, a doctrine of local situations for mental attributes which has hardly died out up to the present time. The conceptions of the phrenologists are merely a development of this sort of thing, very different, however, from what is known as the localization of cerebral function. The liver and love were associated as late as Shakespear's time, when Pistol avers that Falstafl loves " with liver burning hot."*
Galen is responsible for the well-known doctrine of the four temper-
»" Merry Wives," Act 11., Sc. I.
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