ronger than Nurture within the limited
range that I have been careful to assign to the latter.
The effect of illness, as shown by these replies, is great, and well
deserves further consideration. It appears that the constitution of
youth is not so elastic as we are apt to think, but that an attack,
say of scarlet fever, leaves a permanent mark, easily to be measured
by the present method of comparison. This recalls an impression made
strongly on my mind several years ago, by the sight of some curves
drawn by a mathematical friend. He took monthly measurements of the
circumference of his children's heads during the first few years of
their lives, and he laid down the successive measurements on the
successive lines of a piece of ruled paper, by taking the edge of
the paper as a base. He then joined the free ends of the lines, and
so obtained a curve of growth. These curves had, on the whole, that
regularity of sweep that might have been expected, but each of them
showed occasional halts, like the landing-places on a long flight of
stairs. The development had been arrested by something, and was not
made up for by after growth. Now, on the same piece of paper my
friend had also registered the various infantile illnesses of the
children, and corresponding to each illness was one of these halts.
There remained no doubt in my mind that, if these illnesses had been
warded off, the development of the children would have been
increased by almost the precise amount lost in these halts. In other
words, the disease had drawn largely upon the capital, and not only
on the income, of their constitutions. I hope these remarks may
induce some men of science to repeat similar experiments on their
children of the future. They may compress two years of a child's
history on one side of a ruled half-sheet of foolscap paper, if they
cause each successive line to stand for a successive month,
beginning from the birth of the child; and if they economise space
by laying, not the 0-inch division of the tape against the edge of
the pages, but, say, the 10-inch division.
The steady and pitiless march of the hidden weaknesses in our
constitutions, through illness to death, is painfully revealed by
these histories of twins. We are too apt to look upon illness and
death as capricious events, and there are some who ascribe them to
the direct effect of supernatural interference, whereas the fact of
the maladies of two twins being continually alike sh
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