Page:Popular Science Monthly Volume 21.djvu/62

54 shall not endeavor to epitomize the many arguments pro and con in respect to such views as these, but will merely recall, in partial justification of them, the results of some inquiries into the life-histories of twins that I published a few years ago. I took two categories of twins—those who were closely alike in their infancy and those who were exceedingly unlike—and I traced their histories up to the date of the memoir. It appeared that twins who were closely alike at the first frequently preserved their resemblance throughout life, subject, I may almost say, to the accident of a fever, or other serious illness altering the constitution of one of them, and laying the first foundation of a gradually widening divergence. I found not a few cases in which twins residing apart and following different professions at home and abroad still continued to live parallel lives, ageing in the same way, and preserving all along the same features, voice, gestures, and ways of thought. I also met with cases in which death had occurred at nearly the same time to the two twins, and from the same disease. It further appeared, as regards those twins who were born very unlike, that in no case did their dissimilarity lessen under the influence of identical nurture. They had the same nurses, the same tutors, the same companions, they were reared in every respect alike, yet their characters continued to be as dissimilar, and, I need hardly add, their features remained as different as if they had belonged to totally different families. The conclusion to which I was driven by the results of this inquiry was that a surprisingly small margin seemed to be left to the effects of circumstances and education, and to the exercise of what we are accustomed to call "free-will."

It follows from such opinions as these, which appear to be gaining ground in popular estimation, that it is highly desirable to give more attention than has been customary hitherto to investigate and define the capacities of each individual. They form his stock-in-trade, the amount of which admits of definition, whereby he has to gain his livelihood, and to fulfill the claims upon him as head of a family and as a citizen. So far as we succeed in measuring and expressing them, so far almost in an equal degree should we be able to forecast what the man is really fit for, and what he may undertake with the least risk of disappointment. They would encourage him if unduly timid, or they would warn him from efforts doomed to be wasted.

What I propose to speak of in the present memoir are those measurements of the bodily form and faculties that can, or apparently could, be made with some precision, but the personal data in respect. to intellectual and emotional capacities, and to special aptitudes and tastes, require a separate treatment. The progress of the art of measurement of the more purely bodily faculties has been by no means uniform. It has never been specially directed toward furthering the