484 Dynamic Theory. 



tasted, or some of it, must be dissolved by the fluid saliva and mucous 

 of the mouth, and the molecules of the compound thus formed produce, 

 by their contact with the taste papillae, an action which is converted into 

 a nervous electrical movement toward the brain cells. The theory ar- 

 rived at in the case of smell, that separate organs exist for every odor 

 whose sense is conveyed to the brain, applies equally in the case of taste 

 and for the same reason. 



According to Papillon the unassisted organs of taste are capable of only 

 four primitive and original sensations ; viz. , sweet, sour, salt and bitter. 

 If the organs of the sense of smell be out of order or closed up, these 

 four will constitute the sum of taste. Various mixtures of these would 

 givea great variety of tastes, and this variety is greatly increased as 

 well as rendered vastly more refined and delicate by the co-operation of 

 the sense of smell. If this is correct we need not suppose more than 

 four kinds of taste buds. 



Chemical compounds of very different nature have similar taste. 

 Acetate of lead is sweet, while sugar, which is also sweet, is composed 

 of carbon, hydrogen and oxygen. On the other hand, quinine, sulphate 

 of magnesia and others which differ entirely in their composition have a 

 bitter taste. Sweet taste is the opposite of sour and bitter, and the two 

 last may be overcome or smothered by the former either as if the sen- 

 sations in the brain cells interfered with and mutually destroyed each 

 other, or as if chemical action of the two substances in the presence of 

 the saliva of the tongue produced a new molecule having a neutral or a 

 compromise flavor. A saline taste cannot be mitigated by sweet. After 

 tasting a bitter or saline substance, pure water seems sweet, because the 

 water dissolves and removes the cause of the bitter taste substituting a 

 merely negative taste which by contrast appears the reverse of the posi- 

 tive taste. It is a subjective sensation existing only in the brain cells. 

 The acids are generally sour ; the bases or alkalies, caustic. These 

 change in combination with other bodies. The acid and alkaline taste 

 can be produced by the electric current. If the positive pole be placed 

 on the tip of the tongue and the negative on the nape of the neck a cur- 

 rent will pass up the tongue from tip to root and will taste sour. But 

 if the current is reversed by placing the negative pole at the end of the 

 tongue and the positive on the neck, the taste is generally alkaline. 

 Even weak currents produce the effect. If a piece of zinc plate be 

 placed on the tongue and a piece of copper under it in such a way that 

 the metals touch each other over the end of the tongue, a galvanic cur- 

 rent will be generated and an alkaline taste will be perceived. If the 

 metals be reversed the copper above the taste will be acid. 



The sense of taste is probably the youngest of the specialized senses. 

 The condition of its nerve connections would indicate this. The optic, 



