factory membrane.[1] In ordinary breathing, the highest point in the upper stream is, according to Franke, the under edge of the upper turbinal bone, and according to Paulsen and Zwaardemaker, the under edge of the middle turbinal bone.[2] In the rapid and violent breathing with expanded nostrils which we call “sniffing,” the air is carried about 2 mm. higher,[3]—i.e., into the forward and under part of the upper chamber. In either case, odorous particles can reach the olfactory membrane only by diffusion, but more of them will penetrate to it in sniffing than in quiet inspiration. The upper chamber is an annex, not an integral part, of the breathing-passage.
Odorous particles probably do not accumulate in the upper chamber. During inspiration, the air in the passages traversed by the current is thinned, and as soon as inspiration ceases, the air in the upper chamber rushes down to the middle meatus, to be renewed from the pharynx during expiration.[4] If so much odorous matter has been taken in as to saturate the air in the pharynx, we sometimes get a smell in expiration even when we are not eating. Ordinarily, however, the very weak stimulus from the pharynx, coming after the very strong stimulus from without, is not sensed.[5] Fick, indeed, advanced the hypothesis that when odorous particles come in contact with the olfactory membrane, they are at once dissolved in the thin fluid which covers the bottom of the sensitive hairs, and that when so dissolved, they cease to act.[6] These particles may, however, accumulate to some extent on the Schneiderian membrane, especially, if it is in a catarrhal condition, Of course, we get the flavor of food only in expiration. The course of the air in expiration is almost the same. as in inspiration, but Bidder is probably right in supposing that a smaller amount passes above the lower turbinal bone.[7]
Under ordinary conditions, the more rapid the breathing, the more intense the smell, Sniffing is to be forbidden in olfactometric work, not merely because it carries the air higher in the nose, than does “regular breathing,” but because, both by increasing the suction-force and by widening the entrance, it takes more air and therefore more odorous particles into the nose in a given time. The spaces from which air is drawn through the nose are cones with their points at the nostrils. We may see their size and shape in the clouds of vapor formed
