THE SENSE OF SMELL. 



By J. B. Haycraft. 



Contents :— The Anatomical Data, p. 1246— The Passage of Air through the Nose, 

 p 1248 — Olfactometry, p. ] 249 — Hvperosmia and Anosmia, p. 1251 — The 

 Classification of Odours, p. 1252— The Law of Specific Energy of the Senses, 

 p. 1253— The Relationship between Smell and the Chemico-Physical Properties 

 of Odorous Bodies, p. 1254— The Physical Condition of the Stimulant, p. 1256 

 —The Simultaneous Action of Two Odours, p. 1257— The Psychology of Smell, 

 p. 1258. 



Anatomical data.— That sensory surface of the body which is 

 modified in such a manner as to render it impressionable to odorous 

 particles, is found in the upper or olfactory region of the nose. On 

 opening the nasal cavities, the upper region is seen to be lined by a 

 mucous membrane which has a yellow or brown-yellow colour, due to 



the presence of pigment within 

 it. This yellow membrane is 

 generally believed to be olfac- 

 tory, and is so termed. It 

 covers the superior and part of 

 the middle turbinated bones, 

 and that portion of the septum 

 which lies at the same level. 

 Max Schultze 1 was, however, of 

 opinion that the true olfactory 

 mucous membrane, namely, that 

 membrane which contains the 

 olfactory end-organs, has in 

 man a much more limited dis- 

 tribution, and never reaches 

 even to the lower margin of the 

 superior turbinated bone. This 

 has recently been confirmed 

 by the very careful investiga- 

 tions of A. von Brunn, 2 who 

 finds true olfactory epithelium 

 only on an area little more 

 than 1 cm. across, situated in the upper part of the superior turbinated, 

 together with another area of much the same size upon the septum 

 opposite (see Figs. 446, 447, o). 



1 "Bau der Nasenschleimhaut," Halle, 1862, S. 75. 

 "Arch./, mikr. Anat., Bonn, 1892, Bd. xxxix. S. 632. 



Fig. 446. 



