THE HISTOLOGY OF DISSEMINATED SCLEROSIS. 681 



investigated ; and the cerebrospinal fluid is known not to exhibit the cytological 

 and bio-chemical changes which are so marked in para-syphilitic affections. The 

 investigations of the cerebro-spinal fluid have as yet been very incomplete, and the 

 evidence which tends to prove that it is toxic does not decide whether it is so as a 

 result of the process or whether this toxicity is its cause. 



(vi) The remissions and relapses, therefore, necessitate the assumption of the 

 latent presence of the morbid agent in the body, or, if this is an autogenous toxin, 

 either its intermittent evolution, or its accumulation from deficient elimination. 



Variability of the symptoms. It is a little difficult to explain the mechanism 

 of the fleeting early palsies and psychical symptoms. The possibility of an early 

 dynamic modification of function has already been noted, but the period now 

 referred to is one when presumably structural changes have set in. I consider 

 that the involvement of the psychic areas at such a stage is to be explained in 

 the same way as the affection of the motor areas. In such cases it is possible 

 that the motor area or tract involvement is insignificant, for, if it were the 

 essential lesion, the recovery could never be so rapid. Every movement requires 

 the integrity of a large number of association areas, but we realise this only when 

 we watch a child trying to walk, or a paralysed person trying to move. It is 

 possible, therefore, that in these transient palsies the disturbance is in one of the 

 association paths : with each recurrence of an area in such paths, motor images 

 and memories would be progressively blotted out till the motor area is so cut off 

 from its usual associations that progressive paralysis occurs. So long as an axis 

 cylinder remains, a stimulus is capable of passing. The destruction of the myelin 

 sheath probably results in the increase of the resistance to the passage of any 

 stimulus. If a sufficient number of association areas can be linked up around a 

 particular function, in order to elicit from it a discharge sufficient to overcome 

 this resistance, then remission is possible. By stimulation through suggestion, 

 faradisation, etc., these remissions may be brought about with a success dependent 

 upon the degree to which the paralysis is psychic or motor. In this the extra 

 stimulus is probably gained by the linking up of distantly connected association 

 areas and thus utilising or deviating^ their energy to the desired process. It is 

 also possible that when one path is blocked by disease, others, perhaps not so 

 direct, or possibly new paths, may be opened up. 



The lesions are disseminated through the cerebro-spinal axis and disturbances 

 are, therefore, especially liable to affect systems which are extensive. Thus the 

 pyramidal fibres, in their long course from the cerebral cortex to the anterior 

 horn cells in the cord, are invariably and usually early affected : this affection 

 may at first be so slight as to be evidenced only in a unilateral loss or diminution 

 of the abdominal reflexes, or it may be so severe as to give a spasticity great 

 enough to abolish the deep reflexes. As the co-ordinating system has peripheral, 



