Page:American Journal of Sociology Volume 10.djvu/844

 828 THE AMERICAN JOURNAL OF SOCIOLOGY

cence the absorptive surfaces of the canal increase less than the body surface, and, if so, this suggests increased animal food in the past, at the phyletic correlate of this age." The spleen and pan- creas grow rapidly at adolescence. The thymus and thyroid glands, on the other hand, rapidly decline in size, and can safely be extir- pated after, but not before, pubescence.

The growth of the brain at this age consists chiefly in an increase in functional complexity. At puberty changes in mass pass over into involution of texture and increase in complexity of nerve- connections and ultimate ramifications.

(The author quotes, apparently with approval, Aristotle's dictum that the training of the reason should properly begin at the age of fourteen, and adds the modern argument that the histology of the brain reveals the fact that what Flechsig has called the higher or association areas of the cortex undergo a marked acceleration in their growth at this period. But it would not necessarily seem to follow from this that " thought is more independent of muscular activity or motor innervation than we had considered it to be." All this is quite consistent with even a greater emphasis than in the past has been placed upon the importance of the efferent or motor factor in thinking processes. Instead of these facts of the direct connection between the growth of reason and the development of these associa- tion areas militating against the doctrine that we attend and think with our muscles, it rather supports that doctrine, disclosing as it does the inner equating mechanism by which are set up those mutual inhibitions by which incipient muscular movements are directed to finer issues to those finer issues which, in contrast with grosser overt acts, we call the activities of thought or reason.)

" The age of sexual maturity is marked by an outburst of muscu- lar growth, and also by great changes in its direction and distribu- tion," suggesting a close relation between sexual and motor vigor. There is a distinct pubertal acceleration in strength of muscles. Boys almost double their strength between eleven and fourteen. But this growth of muscle-power is not steady and constant ; on the con- trary, there are periods of augmentation and diminution. As a consequence of this unequal development of the motor functions,

this is the age of wasteful ways, awkwardness, mannerisms, tensions that are a constant leakage of vital energy .... motor co-ordinations that will need

laborious decomposition later As from the years of four to eight there

is great danger that overemphasis of the activities of the accessory muscles