TONGUE AND TASTE NOSE AND SMELL 199 



stance frequently suggests the taste, and the taste sometimes suggests the 

 odour. When the sense of smell is temporarily destroyed during a severe cold, 

 taste is often partially or entirely lost until the sense of smell returns. This 

 explains also the common practice of holding the nose while taking a dose of 

 nauseous physic. 



The organ of smell is the mucous membrane which lines the 

 surfaces of the ethmoid bone, this portion only of the nasal cavities 

 being supplied by filaments of the olfactory nerves. 



Fig. 182. Nerves of the Outer Wall of the Left Nasal Cavity. 



During ordinary breathing through the nose, the air passes 

 gently through the lower and wider portions of the nasal cavities, 

 without disturbing to any great extent the air which is enclosed 

 by the scroll-like folds of the turbinated bones. Consequently, 

 even though the air may contain particles of odorous matter, few 

 or none of them come into contact with the terminations of the 

 olfactory nerve, and little or no sensation of smell is experienced. 

 When we wish to perceive an odour more distinctly, we 'sniff' 

 the air. In doing this we close the mouth so as to direct the 

 whole of the inspired air through the nose ; and then draw in the 

 air by repeated short and sudden inspirations. This causes up- 

 ward and abrupt rushes into the nasal cavities, the effect of which 

 is to disturb the comparatively still air of the olfactory part of the 

 nose, and to exchange some of it for the air containing the odorous 

 substance. As soon as the particles of this substance touch the 



