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The Journal of Heredity 



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ONLY THE RIGHT TOES WEBBED IN THIS FAMILY 



Only the second and third toes on the right foot are united. (1 ) number of sons unknown, all 

 normal; (2) number of sons unknown, all with webbed toes. In this case the character is sometimes 

 inherited by the women, but it is only transmitted by the men. Redrawn from Sommer.' (Fig. 



13.) 



Other forms of syndactyly, a suggestion 

 which should be welcomed, in view of 

 the differences in origin in the various 

 types of syndactyly. 



Zygodactyly is not restricted to 

 man; it is found in many mammals, 

 such as several groups of marsupials 

 and in the Simangs, apes from Suma- 

 tra and the Malay Peninsula. In these 

 animals skin-fusion between the second 

 and third toes is a constant occurrence. 

 Figure 8 shows this in a Simang in a 

 late stage of prenatal development, 

 proving again that zygodactyly is a 

 congenital condition. In the large 

 majority of the reported cases of zygo- 

 dactyly of the human foot the fusion, 

 as in the mammals just mentioned, 

 exists between the second and third 

 toes only. For instance, in the 8 

 individuals with zygodactyly, found 

 by Schurmeier^ among a total of 20,000 

 men examined, the anomaly occurred 

 always between toes II and III. It 

 seems highly probable, therefore, that 

 these two toes possess a special ten- 



dency or predisposition to fuse. As 

 shown above, in early development 

 the normal webbing is more pronounced 

 or persists slightly longer between 

 these two toes than between the others. 

 It is also known that the tendon for 

 the long extensor muscle of the toes is 

 split farther up between the third and 

 fourth and fifth toes than between the 

 second and third, another fact pointing 

 towards a greater unity between the 

 last mentioned toes. Weidenreich 

 found in two adults with zygodactyly 

 of these two toes that the tendons of 

 the extensor digitorum longus muscle 

 for toes II and III were in common, or 

 unsplit, for an unusually long distance, 

 i.e., to the middle of the dorsum of the 

 foot. This finding was confirmed by 

 the author in the case of a zygodactyl 

 newborn (fig. 10). 



A number of cases have been de- 

 scribed in which zygodactyly between 

 the second and third toes was asso- 

 ciated with zygodactyly of varying 

 degree between the third and fourth 



^Schurmeier, H. L. 1922. 

 POL., vol. V, pp. 51-60. 



Congenital deformities in drafted men. Am. J. OF Phys. Anthro- 



