AcCORDING tO Jensen, Camarata and HuggiDs quoted by Huggins (1949), sera from cancer patients are generally less effective than normal sera for reducing 2, 3, 5-triphenyltetrazolium chloride (TTC) Method.Serum (0-1 ml.) was mixed with 0-1 per cent TTC reagent (2 ml.) in a pyrex test tube (I cm. diameter), NIIO KOH (I ml.) was added and the mixture heatedon a water bath at 80 ± 0-5' C. for 10 minutes. The reaction mixtureg (which include a blank containing 0-1 ml. -of water instead of serum) were chilled in cold water and then poured into tubes containing glacial acetic acid (1 ml.). The mixtures which had a pH of about 2 -5 were polarographed as f-611ows, : The test solution, into which dipped a dropping mercury cathode, was connected to a saturated calomel reference anode (S.C.E.) by salt-agar bridges (saturated KCI in 3 per cent agar-agar) and the solution deoxygena-ted by passing a stream of water-washed oxygen-free nitrogen through it for 10 minutes. The dropping mercury electrode had the following characteristics: at 20T, in 0.1 N KCI (open circuit), m 0-003118 g./sec. and t = 1-83 sec, with head of mercury, 50 cm. (For explanation of the polarographic terms and procedures, see MiiHer, 1951.)