TASTE, SMELL, AND HEARING 331 



9. Inflammation of the throat may extend into the middle 

 ear and produce an earache. 



10. Enlarged tonsils and adenoid vegetations are the two 



principal causes of earache and deafness. 



1 1. Running ears should be kept clean. 



12. In all animals having a hearing apparatus, the essen- 



tial and often the only part is the inner ear. 



DEMONSTRATIONS 



130. Examine the tongue of one of the pupils. Notice that its sur- 

 face contains three kinds of projections. There is a V-shaped row of 

 large, flat, and smooth projections upon its back part. There are red 

 pinhead-sized projections scattered over the whole front surface. There 

 are also fine projections like velvet spread over the whole surface. In 

 all these projections the nerves of taste seem to end. Examine also a 

 cat's tongue, and note the stiff hairs upon its surface. 



131. Test the power of taste in different parts of the tongue. Place 

 a bit of a sweet or of a sour substance in the back of the mouth, and notice 

 the slight taste, while it is easily tasted in the front part. Now place 

 some salt or bitter substance upon the front of the tongue. Notice that 

 it has little taste until it spreads to the back part. 



132. Saw lengthwise through a calfs head so as to open the nose. 

 Notice the smooth inner surfaces of the nostrils, and their furrowed 

 outer surfaces produced by the folded bones. Notice that the nostrils 

 open into the pharynx. (See demonstration 35.) 



133. Have a butcher remove the bone containing the middle and 

 internal ear from a calf's skull. Carefully cut away the shell of bone 

 over the middle ear. One can judge of its position by measuring down 

 the outer air passage. Notice the size and shape of the middle ear. 

 Notice the ear drum, and the three little bones which stretch from it 

 entirely across the cavity. Notice also that the last bone fits into the 

 small opening leading into the inner ear. 



134. The inner ear will be more difficult to show, for it is small and 

 complicated, and is situated deep in a very hard bone. Cut away the 

 bone a little farther in, when the cochlea may be opened, and possibly 

 a semicircular canal will be recognized. The spiral tube of fhe cochlea 

 is barely of an inch in diameter, while the semicircular canals are as 

 small as a sewing needle, but yet form loops about f of an inch across. 



