THE HUMAN BRAIN

Evening Star, Issue 20117, 6 March 1929, Page 7

THE HUMAN BRAIN

SIR ARTHUR KEITH OH! ‘ NATURE'S MASTERPIECE ' In the second lecture of a course given in tho theatre of the Royal College of Surgeons, Sir Arthur Keith said that man’s brain, with all its failings, represented Nature’s masterpiece. Recently a distinguished Viennese neurologist, Professor Coifstantin Economo, had made a more exact census than any made hitherto of the living units within,the cortex, or rind, which was the essential part of the human brain. He found that a European with a brain of 48oz, which was a common size, had in the neighbourhood of 14,000.000,000 living units, or neurons, as they were named, in the gvey matter or cortex of his brain. The average man, if he were to share out his cortical neurons, could afford to give seven to every human being now alive, and yet have some over. A hallpenny postage stamp, when placed on the surface of the brain, covered an area of cortex which contained a population three times that of Greater London, and it took more than 500 such stamps to cover tho whole area of the unfolded cortex. Tho wires, or nerve fibres, of the brain were living filaments drawn from the bodies of the neurons. A neuron might have as many as 100 filaments, or wires, attached to it—the most of them having- terminals in the neighbourhood and usually one long process or filament to make distant contacts. The degree to which the human brain was “ wired ” would be appreciated when it was remembered that the bodies of the neurons, or living, ceils, made up only 4 per cent, of brain matter, the filaments being responsible for 70 per cent. Yet the whole of this vast population of neurons, each linked up to many neighbours, both near and distant, was set up successfully in most human heads, and in point of efficiency gave a lead which modern telephone enterprise might well essay. If an engineer thought of an organ wired as the brain was, with messages volleying along eacli wire at a rate of some forty or fifty a second and travelling at a rate of 200 miles an hour, he would have some faint conception of the tide of traffic handled by an efficient brain in the course of a morning. A DELICATE FRAMEWORK. The neurons of tho brain had to he fed regularly and supplied with oxygen every minute of the day and night, and their effete products had constantly to be removed. All these elements had to he built into and supported by a delicate framework known as neuroglia. Hence, the brain was not only made up of nerve work, but of a supporting framework and vascular channels of divers sorts. These, with the blood, cerebro-spinal fluid, and outer wrappings of the brain, made up fully 25 per cent, of what filled the skull and was usually called “ brain.” It was plain that mere mass, must be a very insecure guide to capacity. A brain might have mass and yet lack organisation or fail in a hundred other ways. A large body, just as a large city, required a more extensive system of communication and government than a smaller body or city; the brain of the elephant and of the whale far exceeded man’s brain in mass, but in their case the neurons were of a vegetative order. It was not the number of neurons which mattered, but the extent to which the brain was wired. Yet the fact remained that mass of brain did usually count. We were all more or less impressed when we sat down to do business with big-headed men, especially if tlicv- had also strong bodies and a powerful expression. •It was true that sonic of the extinct races of mankind had large brains, but a survey of all the evidence assured us that man’s evolution had been attended by an increase in mass of brain and of intelligence. Intelligence in children usually improved as the brain grew. If the human brain tell short of 320 z its owner was an imbecile: to this no exception had been known. Craniometrical investigations had shown that, in all gatherings made up from our loading men, the average mass of brain was distinctly higher than that of groups which represented manual labourers.