Henry Oldenburg wrote to Leeuwenhoek requesting that he examine hair

February 13, 1676

Oldenburg wrote this letter on 3 February 1676 O.S. to request that Leeuwenhoek turn his attention to hair, which also interested Robert Hooke. Hooke had observed and drawn some hair in Micrographia (Observ. XXXII. Of the Figure of several sorts of Hair, Scheme V, Figs. 2 and 3., p. 155; below right; click to enlarge), though in not nearly as much detail as Leeuwenhoek could with his stronger lenses. At the beginning of his letter of 1676-02-22, Leeuwenhoek replied:

I received your letter of February 3rd in good order, from which I learned that Monsr. Hooke spoke about the hair to you. I shall be pleased to learn about our differences. When I shall be better informed, I am quite willing to give up my opinion and to accept Mr. Hooke's view. Please give him my best regards. I look forward meanwhile to receive by ordinary marketboat the Transactions Nos. 113 and 117 and the following that may be issued.