172 THE POPULAR SCIENCE MONTHLY,
lar system. For the present I neglect the absolute distinction there really is between mental and nervous states.
Beginning with evolution, and dealing only with the most conspic- uous parts of the process, I say of it that it is an ascending develop- ment in a particular order. I make three statements, which, although from different stand-points, are about the very same thing : 1. Evolu- tion is a passage from the most to the least organized — that is to say, from the lowest well-organized centers up to the highest least organized centers. Putting this otherwise, the process is from centers compara- tively well organized at birth up to those, the highest centers, which are continually organizing through life. 2. Evolution is a passage from the most simple to the most complex ; again from the lowest to the high- est centers. There is no inconsistency whatever in speaking of centers being at the same time most complex and least organized. Suppose a center to consist of but two sensory and two motor elements, if the sen- sory and motor elements be well joined, so that " currents flow " easily from the sensory into the motor elements, then that center, although a very simple one, is highly organized. On the other hand, we can conceive a center consisting of four sensory and four motor ele- ments, in which, however, the junctions between the sensory and the motor elements are so imperfect that the nerve-currents meet with much resistance. Here is a center twice as complex as the one pre- viously spoken of, but of which we may say that it is only half so well organized. 3. Evolution is a passage from the most automatic to the most voluntary. The triple conclusion come to is, that the highest centers, which are the climax of nervous evolution, and which make up the " organ of mind," or physical basis of consciousness, are the least organized, the most complex, and the most voluntary. So much for the positive process by which the nervous system is "put to- gether " — evolution. Now for the negative process, " the taking it to pieces " — dissolution.
Dissolution being the reverse of the process of evolution just spoken of, little need be said about it here. It is a process of undevelopment ; it is a "taking to pieces "in the order from the least organized, the most complex, and the most voluntary, toward the most organized, most simple, and most automatic. I have used the word " toward," for if dissolution were up to and inclusive of the most organized, etc., if, in other words, dissolution were total, the result would be death. I say nothing of total dissolution in these lectures. Dissolution being partial, the condition in every case of it is duplex. The symptomatol- ogy of nervous diseases is a double condition ; there is a negative and there is a positive element in every case. Evolution not being entirely reversed, some level of evolution is left. Hence the statement " to undergo dissolution " is rigidly the equivalent of the statement " to be reduced to a lower level of evolution." In more detail, loss of the least organized, most complex, and most voluntary implies the reten-