Page:The Harveian oration 1896.djvu/43

ARISTOTLE’'S THEORY OF THE BRAIN 39 was the centre of voluntary movement, sensation, and thought (the same conception is perhaps indicated by the old Greek myth of Pallas Athene springing from the head of Zeus), though inconsistently he retained the old attribu- tion of certain passions to other organs, such as anger to the heart. He showed that all the nerves originated in the brain, either directly or by means of the spinal cord, which he thought to be a conducting organ merely, not a centre. In opposition to this, it should be remembered, was the theory of Aristotle, who held that the heart was the seat of the sensitive soul with its correlative voluntary movement, and that what we should call nervous action originated there, while the brain was of secondary impor- tance, being the coldest part of the body, devoid of blood, and having for its chief or only function to cool the heart. Aristotle’s reasons for adopting this unfortunate miscon- ception of the brain have been much discussed, and are fully stated in Dr. William Ogle’s admirable translation of Aristotle De Partibus Animalium. They were partly positive observations, such as that the brain substance was itself insensitive, and that many animals which could feel and move (our invertebrata) had no brain, and that he could not trace any connexion between the organs of special sense and the brain. But also he was strongly influenced by his metaphysical idea that the ‘sensitive soul’ was indissolubly connected with heat, and therefore could not have its seat in the coldest organ of the body, devoid of blood. One wonders whether, if Aristotle had been a practising medical man or army surgeon, accustomed to study the effects of blows on the head, he would ever have propounded this theory '.

1 Aristotle’s reasons for rejecting sensation.

the older doctrine that the brain was the seat of ‘the sensitive soul’ are thus stated by Dr. W. Ogle (Ox the Parts of Animals, Notes, p. 172): (1) The brain is itself insensitive. (2) Many animals (viz. our inverte- brata) have no brain and yet have (3) The brain was, as he thought, bloodless. (4) He could trace no anatomical connexion be- tween the brain and the organs of sense. (5) He believed he had good grounds for considering the heart to be the sensory centre.

I think there should be added