T. Lewis and D. Embleton 
41 
the present nomenclature that confusion is unavoidable. " Perodactjly," " Pero- 
manus," " Peropod," " Perochirus," " Ectrodactyly " ; " club-foot," " split-foot," " crab 
or lobster claw," and the foreign equivalents " Hummer-Schere," and " main ou pied 
en pince de homard " are a few of its more simple designations. Many of these 
terms are applied to a variety of malformations and none are sufficiently compi-e- 
hensive as descriptive terms. We are not concerned with any other class of 
sjjlit-hand or split-foot but that of which the " G " family presents examples, and in 
consideration of the constant and fundamental character of the foot lesion*, the 
term " Hereditary Split-foot " is proposed for this deformity f. The term is perhaps 
insufficient in that it contains no reference to the defect of the hand, but the 
variability of the latter is so great that no adequate term is possible without 
lengthening it to an undesirable extent ; moreover there are cases in which there 
is no defect of the upper extremities. 
The nature of the cross-bones. This is a subject of very considerable interest, 
and particularly in the " G " family. What may be termed the clean form is 
illustrated in Figs. 6, 7. These straight bars of bonej have shafts with concave 
borders and end in articular surfaces, each of which may in young subjects be 
shown to have developed from a special epiphyseal ossification centre. In older 
subjects there are indications of the same. A cross-bone has not been met with 
in a sufficiently young hand to enable us to identify the centres of the shaft, but 
in some there is an indication of its double origin (Fig. 12). The outer articu- 
lation is a triple one in which the base of the 1st phalanx and the head of the 
metacarpal bone take part. The cross-bone may bridge over the space between 
the heads of the 4th and 5th (Fig. 6), or the 3rd and 4th (Figs. 14, 19) meta- 
carpals. The outer extremity of the cross-bone has two facets, the inner 
extremity one facet, which may or may not be in contact with the head of the 
metacarpal corresponding ; in the latter case the articulation is with the side of the 
head or shaft of the cross-bone. The type illustrated in Figs. 6 and 7 occurs in 
the hand of IV, 17 (Fig. 11) and in both the hands of V, 39 and 41, the children 
of IV, 23. Articulating with the 3rd and 4th metacarpals it occurs in both hands 
of another member of the same family, namely V, 45 (Fig. 14), and in one hand of 
V, 42 (Fig. 19), and V, 24. These two types have been found in no other 
members of the "G" family. The irregular forms occur in IV, I7's right hand 
(Fig. 10) and in both hands of V, 40 (Figs. 12, 13). Thus cross-bones are limited 
in this family, so far as we are able to judge, to IV, 17, her eldest child, and her 
brother's children, but from the description of their father's hands (III, 2) it 
appears probable that he was similarly deformed, and also other children of IV, 17 
* The constancy of the foot deformity as opposed to that of the hands may possibly be associated 
with the phylogenetic evolution of the extremities. The feet being considered as undergoing retro- 
gressive and the hands progressive development. 
t The term has the additional advantage of being in unison with the German appellation " Spalt- 
Fuss." 
t Which are now recorded for the first time. 
Biometrika vi 
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