1 88 HEREDITY AND EUGENICS 



seven of the thirty- five, both twins " suffered from 

 some special ailment or had some exceptional 

 peculiarity. Two twins at the age of twenty-three 

 were attacked by toothache, and the same teeth had 

 to be extracted in each case." A pair of French twins 

 who travelled as business men and were asthmatic 

 always had attacks in the same cities. They were 

 taken simultaneously with rheumatic ophthalmia 

 (an inflammation of the eye), one in Paris, and the 

 other in Vienna. In another French case the twins 

 were monomaniacs, melancholy, morose, suffering 

 from imaginary persecutions, etc. They showed 

 precisely the same symptoms, although always kept 

 apart and never communicating with each other. 

 At intervals of months the same mental changes 

 would spontaneously come over them both inde- 

 pendently, even when they w^ere in institutions some 

 miles apart. 



In eleven of the thirty-five pairs of twins cited by 

 Galton there was the same association of ideas, twins 

 often making the same remarks on the same occasion, 

 or beginning to sing the same song at the same time. 

 One twin visiting Scotland bought a set of champagne 

 glasses as a surprise for his brother B. The brother 

 in England at the same time bought a set of precisely 

 the same pattern for his brother A. In sixteen cases 

 the twins were closely similar in tastes and dis- 

 positions. The differences in the others were merely 

 in intensity or energy, one being more vigorous, the 

 other more gentle, etc. The mental similarities 

 evidently extended to the fundamental structure of 

 the mind, and were not merely superficial. In only 

 two cases was a strong bodily resemblance accom- 

 panied by mental diversity, and the converse occurred 

 only once. Clearly a more extended study of the 

 mental differences between identical twins will throw 

 valuable light on questions of mental inheritance. 



