My dear Darwin

A curious and, it may be, very interesting result delays my tranfusion experiments.¹ It is that 2 &, I think all 3, of the does that had been coupled with the largely transfused bucks, proved sterile! Of course the sterility may be due to constitutional shock or other minor matters but, it suggests the idea that the reproductive elements are in that position of the blood which I did not transfuse;—to wit, the fibrine.² In my earlier experiments, the blood was only partially de-fibrinised,—hence I was able to get a white leg;—but in these later ones it was wholly de-fibrinised. It seems reasonable that the part of the blood which does most in the reparation of injuries, should also be the most rich in the reproductive elements.

Of course I go on with the experiments & modifications of proceedure. Thus, I hope to succeed in making the ears of two young rabbits grow together & to mix their circulations by breaking adjacent veins into one.³

I wish I had more to tell you. I have transfused into 32 rabbits, in 6 case twice over—Experimented in 6, and killed 43 others to get at their blood;—making a total of 81 killed & wounded, animals—poor things.

Very sincerely yours | Francis Galton