i5G PEOP. B. C. A. WTNDLE ON TEEATOLOGICAL EVIDENCE 



idiots twinning is also found to be very frequent. (3) In families, 

 when twinning is frequent, bodily deformities (of defect and 

 excess) likewise occur with frequency." This last conclusion 

 points in the direction of the blastogenic nature of twinning. 



Those who hold the opinion that the mother's state of 

 nutrition may be a potent factor, may derive some support 

 from Dr. Matthews Duncan's conclusion, drawn from numerous 

 statistics *, that " the largest number of twins is produced by 

 women of from twenty-five to twenty-nine years of age f ; 

 and on each side of this climax of fertility in twins there 

 is a gradually increasing falling- off in their number as age 

 diminishes on the one side, and increases on the other." That 

 nutrition has at least a large influence in the determination of 

 sex, is a proposition supported by Greddes and Thomson J ; and, 

 as they appropriately ask, and the question might equally apply 

 to the subject of twins, were nutrition j)roved to be a factor in 

 its production, " How does Weismann explain the determination 

 of sex, which illustrates an outside influence penetrating to the 

 reproductive ceils ? " It may just be noted, in connection with 

 this subject, and with the last-named authors' view that superior 

 nutrition tends to the production of the anabolic female sex, that 

 the larger number of twins belong to that sex. To sum up this 

 subject, it must unfortunately be said that beyond the statement 

 that twinning is hereditary, it is impossible, in the present 

 chaotic state of statistics on the subject, to draw any definite 

 conclusions in favour of either side of the argument. 



Having disposed of these points, I may now proceed to the 

 other malformations partaking of the nature of excess. 



'Polydactyly. — This is one of the most strongly hereditary forms 

 of malformation. Broca § and M'^Kellar || have both recorded 

 cases where it has passed through six generations, and Muir % 

 one through five. One of the most completely recorded cases 

 is that by Clement Lucas, which is here reproduced (p. 457) **. 



* 'Fecundity, Fertility, and Sterility' (Edinb. 1871), p. 100. 

 t Nutrition being probably at its best during those years. 

 X ' The Evolution of Sex ' (London, 1889), p. 53. 

 § Acad, de M6d. Paris, quoted in Lond. Med. Eec. vol. vi. p. 91. 

 II Glasgow Med. Journ. May 1870. 

 ^ lb. vol. xxi. p. 420. 



** Gruy's Hospital Eeps. vol. xxv. Abbreviations: T.=toes; F. = fingers 

 ea.=;both members affected ; s.p. = sine prole ; X =affeeted. 



