THE SENSE OF HEARING 317 



papillae contain taste beakers, true gustatory organs. They 

 are ovoid collections of cells beneath the epithelial covering of 

 the mucous membrane. Sapid substances enter these beakers 

 in solution and come in contact with the taste cells, which are 

 connected with the filaments of the gustatory nerves. Thus 

 are produced specific impressions which are conveyed to the 

 gustatory center, and the sense of taste is excited. The limited 

 distribution of the taste beakers makes it impossible that they 

 should be the only organs capable of receiving special gustatory 

 impressions. The taste center has been indefinitely located in 

 the uncinate gyrus near the olfactory center. 



Since it is necessary to the tasting of substances that they 

 come in actual contact with the taste organs, and since to do so 

 they must be in solution, it follows that dryness of the mouth 

 interferes with, or abolishes, this sense. 



The most marked tastes are the sweet, bitter, saline, and al- 

 kaline. The more delicate flavors involve also the special sense 

 of smell, and it has been seen that dissociation of the two kinds 

 of impressions is often impossible. Taste is also subject to 

 variations by reason of education, age, association, caprice, etc. 

 Bitters are most easily appreciated at the back, salts and sweets 

 at the tip, and acids at the sides at the tongue. 



5. The Sense of Hearing. 



The ear consists of a complicated apparatus for the purpose 

 of the reception of special impressions which are appreciated by 

 the brain as sounds. Anatomically it consists of the external, 

 the middle and the internal ear; the last contains the essentials 

 of the auditory apparatus, the external and middle divisions 

 serving only to concentrate the sound waves upon the parts of 

 the internal. 



The External Ear. This consists of the pinna and the ex- 

 ternal auditory canal. The pinna is the external visible por- 



