EVOLUTION AND DISSOLUTION, 171 



EYOLUTIOJSr A]S"D DISSOLUTIOIS' OF THE KEEYOUS 



SYSTEM.^ 



By J. HUGHLINGS JACKSON, M. D., F. E. S. 



MR. PRESIDENT AND GENTLEMEN : The doctrine of evo- 

 lution daily gains new adherents. It is not simply synonymous 

 with Darwinism. Herbert Spencer applies it to all orders of phenom- 

 ena. 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 con- 

 sidering them as reversals of evolution — that is, as dissolutions. Dis- 

 solution 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 drunk- 

 enness, 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 f 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 en- 

 tirely 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- 



* This is the first of the Croonian Lectures, delivered before the Royal College of 

 Physicians by J. Hughlings Jackson, M. D., F. R. S., Fellow of the Royal College of 

 Physicians, Physician to the Hospital for the Paralyzed and Epileptic, and to the London 

 Hospital. 



f " Stimulants and Narcotics." 



