Your obliged and obedient Servant. Richard Grindall. L. _A Letter to the Rev._ Tho. Birch, _D.D. Secret. R.S. from_ John Pringle, _M.D. F.R.S. inclosing Two Papers communicated to him by_ Robert Whytt, _M.D. F.R.S._ [Read Dec. 15, 1757.] Pallmall-Court, St. James’s, Dec. 10. 1757.