Ascorbic acid and phosphorous-free protein preponderate in the absorption of u.-v. light by human cerebrospinal fluid. As- corbic acid was shown to prevent the color reaction of Dische''s reagent with thymonucleic acid. The presence of uric acid could not be demonstrated in the spectra of C.S.F. ultra-filtrates. The use of intravenous Na pentothal as an anesthetic did not influence the spectrum of the C.S.F.