332 THE POPULAR SCIENCE MONTHLY, 



some would sink to street-sweepers and sewer-cleansers. But the high- 

 est went progressively higher, and the whole became progressively 

 grander. We are saved from the real as well as apparent degradation 

 of these lower functionaries, only by the fact that the constituents can- 

 not in the social organism, as they can in the material organism, be 

 identified with and merged into their functions. Man has, fortunately, 

 many other functions besides his social functions, viz., those higher func- 

 tions connected with his moral nature. 



In all progress, therefore, and as a necessary consequence of the law 

 of differentiation, there is a straight and very narrow way, from the 

 lowest to the highest, or ideal. Thus, in the progress of the organic 

 kingdom from the lowest eozoun to the final term, the ideal, of material 

 evolution — man — there is only one straight and narrow way onward 

 and upward. Any turning off from that way leads, perhaps, to some 

 other excellence, but not toward the highest — not toward man. Once 

 leave the straight way, and there is no getting back upon it. Progress 

 goes on, but only on the path chosen. The law, so far as material evo- 

 lution is concerned, is inexorable. The tree of evolution has but one 

 straight, ascending trunk leading upward to its terminal bud. A grow- 

 ing-point, once separated as a branch, continues, indeed, to grow, but 

 only on its own way. 



The same is true of higher forms of evolution. The progress of 

 evolution of the organic kingdom, completed in man, is immediately 

 taken vip by man and carried forward on a higher plane in social evolu- 

 tion ; and here, again, we find the same law. In the progress from 

 primitive man to the condition of the most cultured races, there has 

 been but one straight and narrow way. Those nations who by difi"er- 

 entiation turned ofi" from that track, have gone each their separate 

 ^vay — some this, some that — but cannot get back, or have not yet got 

 back, on the true line of progTess toward the highest. I do not say, 

 however, that it is impossible to get back, for Reason again comes in to 

 modify the material law and to confer plasticity on the nature of man. 



The same law, again, appears epitomized with terrible significance 

 in the history of each individual human soul. In the progress of the 

 human spirit from childhood to the highest ideal of intellectual and 

 moral culture — the Christian ideal — there is the same straight and nar- 

 row way. If we turn off from that way, it is easy to go on, but alas ! 

 how hard to get back I But for the modification of material laws by 

 the presence of a higher law, it would be impossible. 



(e.) Cyclical 3fovement. — In all evolution the progress which we 

 have illustrated under the last head advances not at uniform rate, but 

 in a succession of cycles by the rise, culmination, and decline, of higher 

 and still higher dominant functions, principles, ideas, etc. Thus, in the 

 individual Imman organism, there rise, culminate, and decline, first in 

 childhood the nutritive functions ; then in youth and early manhood, 

 the reproductive and muscular functions ; and, lastly, in full maturity, 



