THE SPECIAL SENSES 335 



pass through the pharynx into the nose. An apple is, un- 

 der the same conditions, as tasteless as an Irish potato. If 

 the nose is held shut, ground coffee placed upon the 

 tongue loses its flavor and is as tasteless as sand, if the 

 tongue is wiped dry. The way to make these tests is 

 to obtain the articles and have them given to you for tast- 

 ing without knowing which you are getting; then find 

 whether or not you can tell the difference. 



Substances, in order to be tasted, must first be dissolved 

 on the tongue. The tip of the tongue is most sensitive 

 to sweets and salines, the back part to bitters, and the sides 

 to acids. 



605. The Sense of Smell (Fig. 208). In quiet breathing 

 most of the air passes along the lower parts of the nasal 

 passages, just above the hard palate. Fibers of the olfac- 

 tory nerve end mostly in the higher part of the nasal 

 passages. When we wish to test an odor, we sniff, that 

 is, we take a sudden inspiration by jerking the diaphragm 

 down ; a volume of air larger than usual rushing in, more 

 of it passes over the parts of the walls in which the 

 olfactory fibers are located. It is necessary that the sub- 

 stance producing the odor be in a very finely divided 

 condition, probably gaseous. 



606. Smell has its source in the beginnings of the respir- 

 atory passages, just as taste, is at the gateway of the ali- 

 mentary canal ; and just as taste by its influence on the 

 salivary and gastric glands, greatly influences digestion, so 

 the sense of smell greatly influences the respiratory acts. 

 The breathing of a pleasant odor increases the depth of 

 the breathing. Pleasant odors, as of flowers and of fresh 

 country air and of the forest, contribute to our health and 

 well-being. Why do foods lose flavor when one has a 

 very bad cold in the nose ? 



SUBJECT FOR DEBATE. Resolved, That Dr. Oliver 

 Wendell Holmes's assertion is false, viz : If all the drugs 



