The purpose of the p resen t investigation was to m easure olfactory sensitivity by determ ining the thresholds for odor identification be­ fore and after the various brain operations described in the preceding chapters. With the possible exception of those cases undergoing tran s­ orbital lobotomy it was not expected that im pairm ent in acuity would occur. In th is operation the cutting instrum ent might damage the a rea shown by previous re search to be c ritic a l for olfaction, viz., the olfac­ tory bulbs, to such an extent as to leave the patient anosmic or with m ark­ edly reduced sensitivity. It is doubtful whether damage to other parts of the com plicated olfactory pathway would have any m easurable ef­ fect on thresholds.