November 30, 1934
Dear Doctor Pedersen
I was very much interested in the numerous matters in your letter, and only hope that the things I left still to be done did not prove to be a great burden to you.  By this time you have certainly received the manuscript and that will save you the trouble of going over things twice.  I am sorry that the new equilibrium runs showed a drift and I hope it was not great enough to weaken the value of our findings.  Is there any way of estimating the amount of material of smaller and larger molecular size?
I have read Doctor Hamilton's letter and think it might be interesting as a check to try a run on fat-free material as long as come has been offered.  I do not think our preparations contained appreciable amounts of lipoid for we first shook the extract with toluene and then took out an acid precipitable fraction which would remove still more lipoid.  I think the chief impurity likely to be up to 2 or 3 per cent of serum globulin.  Would that be sufficient foraccount for the drift which you observed?
I am glad that we escaped so much rain, but regret that I could not help you with some of the things that still remained to be done.
With cordial greetings from us to you and Mrs. Pedersen,
Sincerely
Michael Heidelberger