CHAPTER VII, 



OF THE SENSES OF TASTE AND OF SMELL. 



The fact of the extraordinary tactile sensibility of the point of 

 the tongue proves conclusively that the cutaneous corpuscules 

 tactile are not special sensitive apparatus. In effect these cor- 

 puscles do not appear to exist in the lingual mucous membrane. 



The sense of touch has not therefore in man, in whom it has 

 especially been studied, any localisation well defined, any 

 specialisation very distinct. We see it also transforming 

 itself in the tongue, passing gradually into the sense of taste. 

 For the papillary projections of the point of the tongue which 

 are so tactile are at the same time gustatory. To convince 

 ourselves thereof we have merely to excite them with a feeble 

 electrical current. The effect however is the same when we 

 merely excite the parts of the point of the tongue which are 

 destitute of papillse. 



So far we know nothing positive with regard to the seat or 

 even the existence of taste among the invertebrates and even 

 among many of the vertebrates. The buccal mucous membrane 

 of fishes is covered with small teeth, pointed and hooked, and 

 seems very ill organised for gustation. The tongue, which in 

 the vertebrates seems to be the special, or the most special, 

 seat of taste is rudimentary and dry in many reptiles. Never- 

 theless the chelonians and the lissards, which chew their food, have 

 a tongue, soft, rich in papillse. 



