4 
48 Split-Hand ami Split-Foot Deformities 
Abnormal intrauterine conditions can consequently be rationally assigned as 
the cause of the deformity only if it be supposed that they are present at this 
early period ; and if it be granted that the origin of the original deformed and 
later members takes place by the intervention of similar agencies, a position which 
is strengthened by considerations already alluded to, it becomes practically certain 
that the process must be regarded as occurring at a still earlier epoch. For 
a deformed man may have as in Mayer's family deformed children by separate 
and normal wives, and therefore the deformity must exist in a potential form 
in the germs of the father. 
In the next section this line of reasoning will be further pursued. 
{g) Origin as a sport. The main alternatives have now been considered 
and, by a process of exclusion and from the outcome of the discussion upon the 
relation of intrauterine conditions to deformities, it may be concluded that the 
factors concerned in the causation of hereditary split-foot exist very early. The 
deformity is in fact a sport, and its association with Polydactyly and syndactyly 
confirms this conclusion. 
Weismann was of opinion that Polydactyly is due originally to a germ 
variation, and considered that it must be so when the deformity is transmitted. 
Windle states that two main views have been held in the case of duplicity, either 
that the deformity has arisen from the inclusion of additional germ plasm, or that 
a fission of formative material has taken place. It might similarly be concluded 
that conditions of deficiency are due to deficiency of germ plasm, or to a failure 
of fission of the formative material. So far as ectrodactyly pure and simple 
is concerned, these explanations might suffice, but in the case of the variety of 
split-foot which we are discussing they are insufficient. For the deformity may 
be associated with Polydactyly, and with bony syndactyly of such a character that 
it alters the whole conformation of the hand. Further they fail to offer a rational 
explanation of the differences found in individual sports, which are in all proba- 
bility collectively an entity. It is in the general conformation rather than in the 
development or non-development of individual bones that the fundamental defect 
lies. The normal regularity of conformation and the morphological resemblance 
of hands and feet can only be explained by assuming that, in addition to the 
presence in the germ cells of determining factors for the constituent parts of the 
extremities, there must exist factors determining the arrangement and growth of 
these, either separately or collectively (cp. Weismann). There is consequently in 
the case of certain deformities a necessity for assuming a defect in those 
factors which govern the conformation of the extremities, when the allocation 
of the origin of the deformity to a particular stage of development is desired. 
Theoretically the defect may arise at any period in the life history of either germ 
cell or in the fertilised ovum prior to its division, or by a combination of certain 
factors in both germs at the time of union. But the latter supposition necessitates 
the superfluous assumption of variation in the germ cells of both parents. Also 
both this and the assumption that the variation may occur in the ovum itself, 
