ON INHERITANCE OF THE DEFOEMITY KNOWN 
AS SPLIT-FOOT OR LOBSTER-CLAW. 
By KARL PEARSON, F.R.S. 
(1) My attention was drawn at the beginning of 1907 to the existence of a 
family in which " split-foot " or " lobster-claw " was an hereditary deformity. I was 
unaware at the time that Dr Thomas Lewis and Mr Dennis Embleton were at 
work on a much more elaborate study of the same subject based on quite different 
material, and when I did know I did not hand over my material to them, as 
I ought properly to have done, because I wanted to ascertain independently to 
what extent simple Mendelism really applied to an obviously inherited and fairly 
simple human deformity. I wanted to convince myself that Mendelism does or 
does not apply to such cases, by handling the material myself and investigating by 
all the means at my disposal the authenticity of the records. At the same time 
my readers will suffer from having nothing like the completeness of detail in my 
case which may be found in the earlier paper of this number. 
The members of the family are scattered through an agricultural district some 
distance from London, and I could only afford the cost of bringing three members 
up to London for radiography. In this matter I must mention my deep indebted- 
ness to Miss C O. Stevens not only for much aid in following up the family history 
from the clue she first reported to me, but also for the arduous task of piloting the 
strangers through the sights of the Metropolis. To Dr Mackenzie Davidson I owe 
the further big debt that, in the interests of science, he gave up a large portion of 
his valuable time to preparing by stereoscopic radiography no fewer than 22 
negatives of the feet and hands of these three individuals. 
Only a few of these radiograms are reproduced in this paper, but the variety of 
positions taken, as well as the stereoscopic nature of the pictures, has enabled my 
colleague, Professor Thane, to give a very complete account of the hands and feet 
of these three individuals. The ever ready aid given by Professor Thane to 
biometric inquiry would be very inadequately expressed by a few lines of thanks 
in a single biometric memoir. 
It would indeed be impossible from Professor Thane's account of these three 
cases to predict the precise nature of the deformity — the presence or absence of 
bones — in other members of the family who have not been radiographed. No 
