AS TO THE HEREDITT OF ACQUIRED CdSTDITIONS. 469 



found. It is very easy to account for them on the hypothesis of 

 mal-development, for in that case they represent the amount of 

 vitality left in the embryonic cells from which the limb should 

 have developed. On this hypotbesis, we should expect to find, as 

 in fact have been found, many degrees of development ranging 

 from minute nodules, representing fingers at one end of the 

 scale, up to extremities of limbs which differ but little from the 

 hand at the other end." 



To conclude this group, without excluding the possibility of 

 cases of perodactyly, originally caused by amniotic bands being 

 hereditary, since there are no data for such a denial, it appears 

 to me, for the reasons given above as well as from those whicb 

 were brought forward when dealing with the subject of Poly- 

 dactyly and amniotic bands, that on the whole it is far more 

 probable that perodactyly is nearly always due to defect of 

 material, and is therefore blastogenic. 



Congenital Luxation of tJie Femur. — This is a condition which 

 requires some consideration, since it is certainly at times here- 

 ditary and since its origin has been very diversely explained by 

 different writers. I_ append, the following hereditary case, doubly 

 remarkable since present on both sides of the house *: — 



M.n. F. X F.n. 



? sex. X 



P. X F. n. F. X M. double 



I luxation 



/^ 



F.X n.M. = F.i]. 



F. = M.X 



cong. shortening I 

 of thighs I 



I \ r I 



F. X M. X ? sex. ? sex. 



both left n. n. 



Professor Bennett, in an address on this subject t, enumerates 

 the following opinions which have been expressed as to its 

 cause. Dupuytren considered it to be due to an original fault 

 of the germ, which, as Bennett says, is " sufficiently vague." 

 Stromeyer attributed it to a disproportion between the head of 



'^ Quoted by Dupuytren from Massiat, Med. Gaz. 1833, ii. p. 570. 

 t Dubl. Med. Journ. Ixxix. p. 11. 



