K. Pearson 
77 
IV. 23)*, and the external and middle cuneiform are wanting, while a rudimentary 
internal cuneiform is present in both feet of IV. 21 ; that this is not seen in IV. 23 
is again possibly due to delayed ossification. 
Hence the second group differs from the first in the suppression also of the first 
digit, and probably a concomitant reduction of the tarsus. The close resemblance 
of the condition in this second group to that exhibited by the hands is obvious. 
All through the deformity is greater in the children than in the mother. 
In the hands, IV. 23, the younger daughter, shows greater degree of reduction 
than IV. 21. The small number of carpal bones in IV. 23 is to be explained how- 
ever by the fact that the child is too young for ossification to have begun in the 
missing elements. The same consideration will account for the absence of the 
pisiform in IV. 21. This does not apply to the metacarpal bones. 
In the feet there is a difference on the two sides. The left foot is slightly more 
reduced in IV. 23 than in IV. 21 ; whereas the right foot is much more defective 
in IV. 21, IV. 23 having the first digit fairly well develojDed. 
In all three the i-ight hand shows a greater degree of reduction than the left, 
expressed in the condition of the metacarpal bones. 
In the mother the left foot may be regarded as being slightly more reduced, as 
indicated by the fusion of the internal and middle cuneiform bones. In IV. 21 the 
reduction is slightly greater in the right foot than in the left ; whereas in IV. 23 
the left foot is the most reduced of the whole series, while the right foot has a well 
developed metatarsal and phalanx to both great and little toes. 
(6) I have delayed referring to my final criticism of the application of 
Mendelian conceptions to cases of abnormality like the present, until I had placed 
before the reader the above accurate account of the nature of the defect in two 
or three individuals. But having done so it seems to me that a very difficult 
question has to be answered. What in a case like this of split hand and foot is the 
Mendelian unit character ? What are the allelomorphs whose combined absence 
or combined presence is impossible in the zygote ? We can understand what is 
meant when an organ is said to be yellow or white, rough or smooth, however 
much we may wish for the use of a quantitative scale of such characters. We can 
understand what is meant by the presence or absence of a given individual bone, 
say the second phalanx of the fifth digit. But in a case like the present we are 
concerned not with a simple unit of any kind, but the absence of a complex of 
even as many as 60 bones situated in four different parts of the body. In other 
cases 10, 20 or 40 bones may be wanting or incompletely developed. It is true 
that these parts are highly correlated, but as we have seen, deformity of the feet 
is not always accompanied by deformity of the hands. Can we look upon the 
character here as built up of a series of coupled characters representing the system 
of bones we have referred to ? If so, how can we explain the variety of detail 
which is to be found within the same family ? How shall we account for other 
It is interesting to the anatomist to note that the tuberosity of the navicular bone has a distinct 
centre of ossification in both feet of IV. 21. 
