April 10
Dear Dr. Heidelberger
I want to thank you personally for the very proactive preface of complement fixation you furnished us yesterday.
I am sending along the papers on reaction-rate according to our aggreement[sic], in which your part is to pick the holes in the argument.
You also promised to send me Kendall's equilibrium treatment of the quantitative theory.
Sincerely.
AD Hershey