XXI. On the functions of some parts of the brain, and on the relations between the brain and nerves of motion and sensation

The difficulties which attend the investigation of the structure and functions of the brain are shown by the ineffective labours of two thousand years; and the first en­deavour of the author is to remove the idea of presumption that attaches to the very title of this paper. Perhaps the enumeration of some of the sources of error which have retarded discovery may be the best introduction and apology. The first impediment to success is in the nature of the inquiry, since extraordinary and contradictory results must be expected from experimenting on an organ so fine as that must be which ministers to sensibility and motion, and which is subject to change on every impression conveyed through the senses. This remarkable suscep­tibility is exemplified in what we often witness; extraordinary results, such as violent convulsions and excruciating pain, from causes which appear quite inadequate. For example, the presence of a minute spicula of bone which has penetrated to the brain, will at one time be attended with no consequence at all; at another it will occasion a deep coma, or loss both of sensibility and motion. Nay, symptoms apparently as formidable will be produced by slight irritation on remote nerves. Seeing these con­tradictory effects, is it reasonable to expect constant and satisfactory results from experiments in which deep wounds are inflicted on the brain of animals, or portions of it torn away ?