54 
Split- Hand and Split-Foot Deformities 
The counts for split- foot families are as follows : — 
Parker and Robinson's. . .16 deformed and 16 normal. 
Ours 44 deformed and 32 normal. 
Fotherby's 16 deformed and 10 + normal. 
Mayer's 12 deformed and 6 normal. 
Thus there is a greater dominance* of the deformed than is to be expected, though 
several of the families are fairly in agreement with the rule. But we have now to 
proceed a little further. 
It has been stated that the original sport should be a heterozygote, but in the 
family of Mayer (Fig. 2), all the members of the second generation show the 
dominant character, namely are deformed. On Mendelian principles this would be 
brought about if the original sport were a homozygote. But if this is assumed 
there is every reason to assume that every original sport of the sort is a dominant 
homozygote also, and this cannot be allowed, as were it so all children of the 
second generations should be invariably deformed, which they are not. Moreover 
it is the I'ule in these families for an excess of deformed individuals to show itself 
in the first generation, and this is the case also with the majority of deformities of 
the hands or feet which run tlirough long families f. 
Lastly if Mendelian proportions are to hold good they must not only hold good 
in every family of the particular deformity examined, hut they must above all hold 
good for each succeeding generation, for upon this depends entirely the question of 
stability, which is the chief point at issue. In families showing split-foot the 
following figures are shown : — 
Parker & Robinson's 
Ours 
Fotherby's 
Mayer's 
D. 
N. 
D. 
N. 
D. 
N. 
D. 
N. 
D. 
N. 
1st gen.i ... 
1 
G 
1 
0 
1 ? 
? 
1 ? 
? 
2nd gen. ... 
9 
4 
11 
3 
] ? 
1 
6 
0 
27 
7 
3rd gen. ... 
7 
12 
1.3 
5 
2 
2 + 
5 
6 
27 
25 
4th gen. ... 
17 
22 
9 
3 
1 
0 
27 
25 
5th gen. ... 
1 
2 
4 
5 
5 
7 
Totals ... 
86 
64 
D. = deformed, N. = normal. 
An examination of these figures shows a decided tendency for the deformity to 
die out. In view of this and of the hyperdominance of the deformity as a whole, 
* A dominance which has already been noted by Bateson in many families, 
t Families illustrating " latency," are not here considered. 
X For convenience sake, the numbering of generations in this table does not correspond with 
that given in Fig. 1. 
