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Correspondence with Charles Darwin   161

standing this, I can assure you that I have the matter firmly in hand, and will be guided by the results, as to the extent of future work. Defibrinised blood is my salvation. I literally put into my silver greys during one operation as much blood as I can get from two rabbits each of the same size as the patient, and I have three bucks who have undergone two operations (but unluckily the earlier ones were far less successful). Very sincerely yours, FRANCIS GALTON.

(10)   42, RUTLAND GATE, S.W. June 25th, 1870.

MY DEAR DARWIN, A curious and, it may be, very interesting result delays my transfusion experiments. It is that 2, and I think all 3, of the does that had been coupled with the largely tranfused bucks prove 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 the portion of the blood which I did not transfuse; to wit the fibrin. In my earlier experiments, the blood was only partially defibrinised,-hence I was able to get a white leg; but in these later ones it was wholly defibrinised. It seems reasonable that the part of the blood which does most in the reparation of injuries should also be most rich in the reproductive elements. Of course I go on with the experiments with modifications of procedure....I wish I had more to tell you. I have transfused into 32 rabbits, in six cases twice over....

Very sincerely yours, FRANCIS GALTON.

The letters now break off, and the Galtons went to Paris on July 15th, intending to go to Switzerland; they did go to Grindelwald, but the declaration of war between France and Prussia led them to return. Here, after a stay at Folkestone, they paid visits to the Gurneys, at Julian Hill, at Leamington and at the Groves, reaching London only on October 17th (L. G.'s Record). On September 27th, George Darwin, however, wrote that his father sent his- thanks for Galton's rabbit message and said that he was deeply interested in the success of the experiment. The nature of that experiment is clear, although Galton's letter detailing it appears to have perished; it is provided by Galton's paper itself; it was to cease defibrinisation, and it was done by establishing cross-circulation between the carotids, the great arteries of the neck.

"If the results were affirmative to the truth of Pangenesis, then my first experiments would not be thrown away; for (supposing them to be confirmed by larger experience) they would prove that the reproductive elements lay in the fibrine. But if cross-circulation gave a negative reply, it would be clear that the white foot was an accident of no importance to the theory of Pangenesis, and that the sterility need not be ascribed to the loss of hereditary gemmules, but to abnormal health, due to defibrinisation and, perhaps, to other causes also.

My operations of cross-circulation (which I call x) put me in possession of three excellent silver-grey bucks, and four excellent silver-grey does    There were also three common rabbits, bucks, which .were blood mates of silver-greys, and four common rabbits, does, also blood mates of silver-greys. From this large stock I have bred eighty-eight rabbits in thirteen litters, and in no single case has there been any evidence of alteration of breed. There has been one instance of a sandy Himalaya; but the owner of this breed assures me they are liable to throw them, and as a matter of fact, as I have already stated, one of the does he sent me did litter and throw one a few days after she reached me. The conclusion from this large series of experiments is not to be avoided, that the doctrine of Pangenesis, pure and simple, as I have interpreted it, is incorrect." (p. 404, loc. cit.)

Galton concludes that the gemmules are not independent residents in the blood; they either reside in the sexual gland itself, the blood merely forming nutriment to the growth, or they are merely temporary inhabitants of the blood and rapidly perish, so that the transfused gemmules perished before the period elapsed when the animals had recovered from their operations. Galton suggests that an experiment might be made-as the -animals

PGII   21