50 
Split- Hand and Split-Foot Deformities 
occasions, has shown variation along lines showing close resemblance. The facts 
are so striking as to suggest that nature's sports are not so erratic as they might at 
first sight seem, hut that they tend to occur in definite directions and along definite 
lines. 
(h) Transmission of hereditary split-foot, its stability, and the relation of its 
mode of transmission to Mendelism. The arguments which assign the origin of 
hereditary split-foot to a sport have been fully considered and we are now in a 
position to discuss the mechanism of transmission from this point of view. In 
dealing with the types and combinations of types sufficient has been said to show 
the similarity of these in different families. In any particular family* it is 
impossible to predict the exact deformity or even the type of deformity which will 
occur in the offspring of an abnormal parent ; all that can be prophesied is that the 
deformed children will conform to one or other of the general types. In a fair 
percentage of cases however direct transmission of a type from parent to offspring 
or indirect to a grandchild through a child of a different type is found. The 
nearest approach to uniformity of type is presented by Maj^er's family in which 
split-hand occurs in almost all the individuals reported ; in one instance through 
three generations. In the same family is an example of a father with both feet 
and the right hand affected transmitting the same defects to his son (Fig. 2, II, 2 
III, 10), also an instance of transmission from father to son of deformity confined to 
the feet (Fig. 2, II, 3, and III, 11). Two examples of the last are also to be found 
in Parker and Robinson's tree. In Fotherby's report Polydactyly occurs frequently 
and is transmitted once. In our own family polydactyly occurs in grandfather, 
mother and daughter (IV, 3; V, 6 ; VI, 1). Transmission missing one generation 
is illustrated in Parker and Robinson's family where three grandchildren " revert " to 
the type of the grandpai-ent who was deformed in all extremities, while the mother 
of the children had perfect hands. The same occurs once in the " G " family 
(II, 2 ; III, 7 ; IV, 31). The limitation of a type to a branch of a family is fairly 
well seen in the occurrence of cross-bones in all the children of IV, 23. But 
although these instances occur with sufficient frequency to merit attention, yet 
there is no constancy of the inheritance of individual peculiarities. 
As these examples are the only striking instances of particular transmission 
happening in the four fully reported families mentioned, it may be said that they 
are the exception rather than the rule. And from the instances cited it follows 
that though examples of direct transmission of types occur too frequently to allow 
of their explanation as coincidental, yet there is little evidence of their transmission 
in a stable formf, and it must be admitted that while a lesser deformity (such as 
that of feet only), may occur, nevertheless the individual shoiuing this lesser 
malformation may transmit the full defect to offspring. The actual deformity in an 
individual is thus no index of the potential deformity transmitted to that individual. 
* In the following, the larger families "u. "s.a.anjii^ ^re alone dealt with. 
+ It is true that examples of split-foot and Polydactyly of the hands are reported in three successive 
generations, yet in no case are the deformities identical. 
