T. Lewis and D. Embleton 
47 
Lastly they might be involved at a very early or at a later period of develop- 
ment. 
The views, which have been held, deal, as may be seen from what has already 
been said, with the origin at a later date. So far as they apply to the origin 
of the malformation in those members of a family who have inherited the defect*, 
they may be at once excluded, for the lesions are in the four extremities in the 
majority of cases ; they are fairly symmetrical ; they are similar in different 
individuals ; there is no evidence of similar and simultaneous affection of any 
other partf of the body; and one of two twins may be alone affected Again 
actual evidence of bands, adhesions, or amputated digits has so far been in no 
case forthcoming^. The argument that there should be transmission through 
the female only is insufficient, for the amnion certainly and perhaps the amniotic 
fluid too is of foetal origin. Lastly the theory involves the supposition that 
acquii'ed characters are transmitted. 
Possibilities 1 and 2 may be considered together, for arguments have been 
already produced to show that all such individuals are examples of an entity, and 
that all such deformities would be transmitted if the opportunity arose §. Now 
if these original members are examined it is found that they differ in no way from 
the later members of families. As a whole they show the same general characters 
and the same variations. And this similarity suggests that a similar fundamental 
factor is at fault in the production of the original and subsetpient deformities. 
But as has been previously stated the mode of origin is not necessarily identical, 
and it can only be stated that in all probability there is much in common in their 
production. Further arguments have consequently to be considered. The evidence 
which refutes the possibility of the origin of deformities in the later members of 
a family in intrauterine lesions applies to a great extent to the original members, 
particularly the symmetry, the quadruple nature of the deformity, the similarity 
of the separate individuals and the absence of evidence of such lesions. And 
these facts are stongly in favour of the existence of the cause, whatever it may 
be, at a time when a common factor may act simultaneously upon four masses of 
formative material, representing the four extremities respectively, or of its existence 
at a time when all four extremities have a common representative. But in any 
case the evidence necessitates the assumption that the cause exists at a very early 
period of development, and certainly prior to the division of the ovum. The great 
functional capacity of the deformed limbs is in itself a proof of the eai'ly laying 
down of the hands and feet in their malformed state. 
* It is to these that the arguments of Perthes particularly apply. 
+ It must be noted that in two single cases the deformity has been associated with deficiency of the 
palate. 
X In the case of J. A. (V, 38) which we have described anything of the kind certainly did not exist. 
§ Weismann criticising Zander's opinion that Polydactyly arises as a result of the action of amniotic 
threads on the finger-buds says that such a view is untenable in cases where there is a hereditary 
history. 
