January 29, 1941

Professor William C. Boyd

Department of Biochemistry

Boston University

School of Medicine

80 E. Concord Street

Boston, Massachusetts

Dear Dr Boyd:

I am very glad to have your comments on our paper. We are changing the wording in just the way that you recommend. It was, of course, wrong for me to write that you failed to verify Landsteiner's observations. Dr. Landsteiner has also written to me that this sentence is incorrect.

I am having Dr. Pressman send some samples of our precipitable haptens to you.

I am afraid that, because of ionization, it would be difficult to obtain freezing point or boiling point evidence regarding the molecular state of our dyes. We have, however, shown that most of the dyes with which we worked pass easily through a cellophane membrane, and that the precipitin reaction can be obtained with material which has just passed through the membrane. The pores in the membrane are perhaps about 30 Å in diameter. It is, of course, possible that the dye polymerizes, and exists in equilibrium with the unpolymerized molecules, which again polymerize after passing through the membrane. Nevertheless the ease of dialysis of the dye suggests that they are not largely colloidal.

I was not suggesting in my letter that you did not publish your observations but rather that your published observations might be interpreted as evidence for the framework theory of agglutination. The first and third paragraphs on page 349 of your 1937 paper on mixed agglutination say that under some conditions separate agglutination of the cells of different types occur and that heterogeneous clumps were obtained only under definite conditions. If the second phase of flocculation were not specific, we might well expect heterogeneous clumps under all conditions, and interpret your observations as evidence against this postulate.

Sincerely yours,

[Linus Pauling]

LP: jr