The observation1,2that the “total neuraminic acid” in the cerebrospinal fluid (CSF) of schizophrenic patients as a group is lower than that found in nonschizophrenic subjects raised many questions regarding the possible significance of this finding. Perhaps one of the first of these is concerned with the constancy of the neuraminic acid concentration in a given patient over a period of time. If the concentration of neuraminic acid is indeed of significance in the schizophrenic process, several possibilities present themselves. The concentration may be a constant characteristic for a given individual—like a fingerprint, a biological landmark. On the other hand, the concentration may vary with different functional states of the nervous system. It is also possible that both phenomena may operate; thus, the concentration may vary slightly with certain functional states, but vary over a relatively narrow range, which is itself in some