Dear Sir,

I think the following case of what must be an hereditary transmission of disease will interest you.

On my father’s side I am a member of a large family.¹ There are about 30 of us in my generation all of us being adults. Out of the 30, there are 10 who suffer more or less from defect in the right knee joint

6 out of the 10 have had positive disease,—the remaining 4 have only weakness in the joint. I had the worst knee of us all and about two years ago I had the limb taken off.

Now neither my Father, nor any of his brothers and sisters nor his father and mother and their brothers and sisters ever had, to my Father’s knowledge, any weakness in their joints nor did my Father ever hear of any of his ancestors having weak joints.

Yet it is clear that the defect is inherited for the ten who have suffered from it comprise members of all branches of the family—six in number—not one branch having escaped. There have been no intermarriages.—

The different branches settled (with the exception of two) in different parts of the Country. Indeed one Branch in which a bad knee appeared about 2 years ago has been living in South Australia for 21 years. I have one cousin who has a diseased left elbow joint, but none of us have anything the matter with the left knee.

I trust you will excuse an entire stranger addressing you. I need not say that I expect no reply.

I must take the opportunity of thanking you for the great benefit I have derived from the study of your works   It is the perusal of your latest which leads me to think of writing.²

I am | Dear Sir | with the greatest respect | Yours faithfully | Lewin Hill

I should add that those of my generation have now 44 children in all, none of whom have yet shown any weakness in their joints.

Charles Darwin Esq | &c &c &c