Two obstacles which confront the student of the olfactory function are, strangely enough, the complexity of the central apparatus and the simplicity of the end-organ. The anatomy of the first cranial nerve and its central tracts and pathways has been minutely described. Concerning their separate functions—if indeed these structures have separate functions—which in the aggregate produce those mental impressions which we interpret as smell, we are in total ignorance.
Tedious and inconclusive experiments were at one time performed on animals, in an attempt to fasten certain smell impressions on given tracts and centers, but the results were so uncertain as to be of little value.
Although the central apparatus consists of a score of nuclei, tracts and fasciculi, which is hardly surprising when one takes into account the complexity of smell impressions, still the peripheral organ in the nose, which records these impressions, is bafflingly simple. Unlike the perception apparatuses