174 THE POPULAR SCIENCE MONTHLY, 



third stage, h^ + m^ + l ', etc. Althougli I shall say very little later on 

 of involvement of middle and lowest centers in cases of uniform disso- 

 lution, it is most important, especially with regard to clear notions on 

 localization, to recognize that the order of dissolution is a compound 

 order. 



The next division is local dissolution. Obviously disease of a 

 part of the nervous system could not be a reversal of the evolution of 

 the whole ; all that we can expect is a local reversal of evolution, that 

 there should be loss in the order from voluntary toward automatic in 

 what the part diseased represents. Repeating in effect what was said 

 on uniform dissolution, it is only when dissolution occurs in all divis- 

 ions of the highest centers that we can expect a reduction from the 

 most voluntary of all toward the most automatic of all. Dissolution 

 may be local in several senses. Disease may occur on any evolution- 

 ary level on one side, or on both sides ; it may affect the sensory ele- 

 ments chiefly, or the motor elements chiefly. It must be particularly 

 mentioned that there are local dissolutions of the highest centers. It 

 will be granted that in every case of insanity the highest centers are 

 morbidly affected. Since there are different kinds as well as degrees 

 of insanity, for examples, general paralysis and melancholia, it follows, 

 of necessity, that different divisions of the highest centers are morbid- 

 ly affected in the two cases. Different kinds of insanity are different 

 local dissolutions of the highest centers. 



I now come to give examples of dissolution. I confess that I have 

 selected cases which illustrate most definitely, not pretending to be 

 able to show that all the diseases of which we have a large clinical 

 knowledge exemplify the law of dissolution. However, I instance 

 very common cases, or cases in which the pathology has been well 

 worked out ; they are cases dependent on disease at various levels 

 from the bottom to the top of the central nervous system. Most of 

 them are examples of local dissolution : 



1. Starting at the bottom of the central nervous system, the first 

 example is the commonest variety of progressive muscular atrophy. 

 We see here that atrophy begins in the most voluntary limb, the arm ; 

 it affects first the most voluntary part of that limb, the hand, and first 

 of all the most voluntary part of the hand ; it then spreads to the 

 trunk, in general to the more automatic parts. To speak of a lower 

 level of evolution in this case is almost to state a barren truism. At 

 a stage when the muscles of the hand only are wasted, there is atrophy 

 of the first or second dorsal anterior horn ; the lower level of evolu- 

 tion is made up of the higher anterior horns for muscles of the arm. 

 This statement, however, is worth making, for it shows clearly that 

 by higher and lower is meant anatomico-physiologically higher or 

 lower. 



2. Going a stage higher we come to hemiplegia, owing to destruc- 

 tion of part of a plexus in the mid-region of the brain. Choosing the 



