| EVOLUTION AND DISSOLUTION OF THE NERVOUS SYSTEM.[1] |
By J. HUGHLINGS JACKSON, M. D., F. R. S.
MR. PRESIDENT AND GENTLEMEN: The doctrine of evolution daily gains new adherents. It is not simply synonymous with Darwinism. Herbert Spencer applies it to all orders of phenomena. His application of it to the nervous system is most important for medical men. I have long thought that we shall be very much helped in our investigations of diseases of the nervous system by considering them as reversals of evolution—that is, as dissolutions. Dissolution is a term I take from Spencer as meaning the reverse of the process of evolution. The subject has been worked at for many years. About half a century ago, Laycock applied the doctrine of reflex action to the brain. Sir Charles Bell, in speaking of degrees of drunkenness, and Baillarger, in remarking upon aphasia, have pointed out that there is a reduction from the voluntary toward the automatic. The late Dr. Anstie's researches[2] are perhaps the most valuable of all contributions toward the study of diseases of the nervous system as examples of dissolution, although he did not use that term. I refer also with great respect to the most valuable and highly original work which Ross, Ribot, and Mercier have done in the same direction. The brilliant researches of Hitzig and Ferrier, besides their obvious great value in other ways, are of very great value in supporting the doctrines of evolution and dissolution of the nervous system. In this connection I gladly mention with great respect a recent valuable paper on cerebral localization by Dr. Sharkey.
Wishing as soon as possible to give illustrations of dissolution, I will make the necessary preliminary as short as I can. I speak only of the most striking aspects of evolution and dissolution, leaving entirely out of account some very important factors specially insisted upon by Herbert Spencer. I regret that time renders it necessary for me to simplify my subject by serious omissions. Spencer, to whom I am under the deepest obligation, must not be judged by my present application of his doctrines, or rather of part of them. I have to ask pardon for the use in this lecture of some popular terms. "Most voluntary," though it has a technical sound, is, when used in contrast to "most automatic," a popular term, and later on it will be discarded. I have also to acknowledge an omission; I speak for the most part of the cerebral system only, almost ignoring all divisions of the cerebel-
