CHAPTER XXX 



TASTE AND SMELL 



Taste. (a) To test the localisation of taste, direct the subject to close his eyes 

 and put out his tongue. This organ is then dried, and different parts are touched 

 with a small brush or a glass rod moistened with the sapid substance in solution. 

 After each observation the mouth must be rinsed with water. The following 

 solutions may be used for testing the four qualities of taste, viz. : for bitter, 1 

 per cent, solution of quinine sulphate ; for sweet, 5 per cent, solution of sugar; 



FIG. 83. ZWAARDKMAKER'S OLFACTOMETEK. , NOSE PIECE ; SCT, SCREEX: 



t, POROUS TUBE SLIDING OVER GRADUATED GLASS TUBE. 



for acid, 2 per cent, solution of citric acid ; and for salt, 5 per cent, solution 

 of common salt. Notice the time which intervenes between the application 

 of the sapid substance and its effect. Record your results as regards localisation 

 upon an outline plan of the tongue. 



(b) Chew a leaf of Gymnema sylvestris, or paint with cocaine solution, and 

 determine whether the taste of any of the varieties of sapid substances is affected. 



(c) Test different parts of the tongue by applying closely-set electrodes arranged 

 to conduct a weak faradising current. 



Smell. The sense of smell is tested by Zwaardemaker's olfactometer, which 

 consists of a glass tube with one end adapted to the nostril, while over the other 

 end a tube constructed of, or impregnated with, the odoriferous substance, 

 slides ; so that a greater or less amount of its inner surface can be exposed to 

 the air which is passing through the glass tube into the nostril (fig. 83). 



Ill 



