Page:Popular Science Monthly Volume 76.djvu/339

Rh matter of course. Its only interest for us lies in the fact that most alterations in the surroundings that are brought to bear upon human beings are probably not very great in actual differences. They are at least not great in comparison with the experiments of the botanist and zoologist. (2) Environmental influence diminishes with increased phylogenetic rank. (3) Environmental influence diminishes with the evolutionary rank of the tissue affected. (4) Environmental influence diminishes in proportion to the age of the tissue affected. The contents of this paper have been chiefly brought forward to support these second, third and fourth laws. Artificial modification then appears to be easiest upon tissues that are either young or simple, or in a condition of cell subdivision and growth. It must be remembered that the brain-cells, even of a child, are, of all tissues, farthest removed from any of these primordial states. The cells of the brain ceased subdivision long before birth. Therefore, a priori, we must expect relatively little modification of brain function. We next have to consider the question of the possibility of escape on the part of the organism from a novel and perhaps unwelcome environment into its natural one again. (5) Environmental influence diminishes with the organism's power of choice. This may be the chief reason why human beings, who of all creatures have the greatest power to choose the surroundings congenial to their special needs and natures, are so little affected by outward conditions. The occasional able, ambitious and determined member of an obscure or degenerate family can get free from his uncongenial associates. So can the weak or lazy or vicious (even if a black sheep from the finest fold) easily find his natural haunts.

In psychological matters we are dealing with a totally different class of cases from the zoological experiments referred to in this paper. It is a point often forgotten, yet one that should be constantly born in mind, that there are these two kinds of environment from the standpoint of an organism. There are surroundings from which there is no escape, let the creature try his best, and there are also environments from which escape is possible if the inheritant desires impel it. All the modifications on lower animals alluded to in this article are of the first kind, or have been brought about by imposed conditions from which there was no escape. Psychological environment can scarcely be placed in the same category. Therefore the inference is that not only is the brain little influenced by surroundings owing to its high