xx Obituary Notices of Fellows deceased. 



His observations of cases of unilateral right-sided convulsions, followed 

 by temporary loss of power and loss of speech, led him to conclude that 

 these were the counterpart of hemiplegia, and dependent, not on destruction, 

 but discharging lesion, followed by exhaustion of the same region. " From 

 the point of view of function there are two ways in which nerve tissue 

 suffers. It may be destroyed, and then there is loss of function. It may 

 be unstable, and then there is disorder of function-discharge. In the case 

 of nervous organs representing movements, we have palsy from destruction, 

 and we have irregular movements (chorea), occasional spasm, etc., from 

 instability " (" A Study of Convulsions," ' Trans. Med. Grad. Assoc.,' vol. o, 

 1870). The region affected he described vaguely as the convolutions 

 related to the corpus striatum, the region supplied by the Sylvian artery. 

 In reply to possible objections on the ground that the cerebral hemispheres 

 were the organ of the mind, he remarks : — 



" It is asserted by some that the cerebrum is the organ of mind, and 

 that it is not a motor organ. Some think the cerebrum is to be likened 

 to an instrumentalist, and the motor centres to the instrument ; one part 

 is for ideas, and the other for movements. It may then be asked, How 

 can discharge of part of a mental organ produce motor symptoms only ? 

 I say motor symptoms only, because, to give sharpness to the argument, 

 I will suppose a case in which there is unilateral spasm without loss of 

 consciousness. But of what 'substance' can the organ of mind be com- 

 posed, unless of processes representing movements and impressions ; and 

 how can the convolutions differ from the inferior centres, except as parts 

 representing more intricate co-ordinations of impressions and movements 

 in time and space than they do ? Are we to believe that the hemisphere 

 is built on a plan fundamentally different from that of the motor tract ? 

 What can an ' idea ' (say, of a ball) be except a process representing certain 

 impressions of surface and particular muscular adjustments ? "What is 

 recollection but a revivification of such processes which, in the past, have 

 become part of the organism itself ? What is delirium, except the disorderly 

 revival of sensori-motor processes received in the past ? What is a mistake 

 in a word, but a wrong movement, a chorea ? Giddiness can be but the 

 temporary loss or disorder of certain relations in space, chiefly made up 

 of muscular feelings. Surely the conclusion is irresistible, that ' mental ' 

 symptoms from disease of the hemisphere are fundamentally like hemi- 

 plegia, chorea, and convulsions, howeA r er specially different. They must all 

 be due to lack, or to disorderly development, of sensori-motor processes " 

 (' Trans. St. And. Med. Grad. Assoc.,' vol. 3, 1870). 



Jackson's views as to the constitution of the cerebral hemispheres and the 

 existence of motor centres for the limbs, face, etc., in the Rolandic area 

 were confirmed by Hitzig (1870) and subsequent experimenters. By his 

 own careful observation of the onset, limitation and march of the spasms in 

 cases of disease, he himself largely contributed to the exact localisation 

 in man of the various motor centres experimentally determined on the lower 



