Among my thirty-five detailed cases of close similarity, there are no less than seven in which both twins suffered from some special ailment or had some exceptional peculiarity.  One twin writes that she and her sister “have both the defect of not being able to come downstairs quickly, which, however, was not born with them, but came on at the age of twenty.”  Three pairs of twins have peculiarities in their fingers; in one case it consists in a slight congenital flexure of one of the joints of the little finger; it was inherited from a grandmother, but neither parents, nor brothers, nor sisters show the least trace of it.  In another case the twins have a peculiar way of bending the fingers, and there was a faint tendency to the same peculiarity in the mother, but in her alone of all the family.  In a third case, about which I made a few inquiries, which is given by Mr. Darwin, but is not included in my returns, there was no known family tendency to the peculiarity which was observed in the twins of having a crooked little finger.  In another pair of twins, one was born ruptured, and the other became so at six months old.  Two twins at the age of twenty-three were attacked by toothache, and the same tooth had to be extracted in each case.  There are curious and close correspondences mentioned in the falling off of the hair.  Two cases are mentioned of death from the same disease; one of which is very affecting.  The outline of the story was that the twins were closely alike and singularly attached, and had identical tastes; they both obtained Government clerkships, and kept house together, when one sickened and died of Bright’s disease, and the other also sickened of the same disease and died seven months later.

Both twins were apt to sicken at the same time in no less than nine out of the thirty-five cases.  Either their illnesses, to which I refer, were non-contagious, or, if contagious, the twins caught them simultaneously; they did not catch them the one from the other.  This implies so intimate a constitutional resemblance, that it is proper to give some quotations in evidence.  Thus, the father of two twins says:—­

“Their general health is closely alike; whenever one of them has an illness, the other invariably has the same within a day or two, and they usually recover in the same order.  Such has been the case with whooping-cough, chicken-pox, and measles; also with slight bilious attacks, which they have successively.  Latterly, they had a feverish attack at the same time.”

Another parent of twins says:—­

“If anything ails one of them, identical symptoms nearly always appear in the other; this has been singularly visible in two instances during the last two months.  Thus, when in London, one fell ill with a violent attack of dysentery, and within twenty-four hours the other had precisely the same symptoms.”

A medical man writes of twins with whom he is well acquainted:—­