968 
Proceedings of the Roycd Society 
It has been assumed by most economists that the “ necessities of 
life ” were simply food, shelter, &c., and that the subtler factors of 
the environment need not be included. This pre-biological concep- 
tion need not be argued with, for the economic problem of the 
maintenance of men is but one special case of the vast problem of 
the modification of organism by environment, exactly as the descent 
of man is a special case of the origin of species. 
§ 33. Mode of Modification of Organism hy Environment . — • 
Although time and space and knowledge do not admit of tracing 
out these lines of modification in detail, some idea of the two main 
lines of evolution and degeneration respectively must be obtained. 
It is convenient to begin with the latter, since the conditions of 
degeneration in the organic world are approximately known. These 
conditions of degeneration are of two very distinct kinds — on the 
one hand, deprivation of food, light, &c., so leading to imperfect 
nutrition and innervation ; on the other, a life of repose, with 
abundant supply of food and decreased exposure to the dangers of 
the environment. It is noteworthy that while the former only 
depresses, or at most extinguishes, the specific type, the latter, 
through that disuse of nervous and other structures, &c., which 
such simplification of life involves, brings about that far more 
insidious and thorough degeneration seen in the life history of 
myriads of parasites. It is noteworthy that both these sets of con- 
ditions of organic change exist abundantly in society, the former 
being known as poverty, the latter as “ complete material well- 
being.” The influence of all this upon the degeneration of indivi- 
duals and upon the decline and fall of nations alike, need not be 
insisted upon. 
Passing now to the less known conditions of evolution as 
opposed to degeneration, it is obvious that (1) adequate conditions 
of food, light, atmosphere, are necessary; (2) that the organism, 
and primarily the nervous system, must be adapted to more and 
more complex conditions of the environment ; ■i.e., that the nervous 
system must become more and more highly evolved. 
Hence arises the physiological explanation of the aesthetic sub- 
function in production, of which we were compelled to notice the 
enormous importance even under the preceding analysis of physical 
principles. It is determined by the need of the various senses, and 
