THE SENSES. 199 



Spallanzani discovered that bats could thread their way with ease 

 through the darkest and most intricate passages, where obstacles 

 had been purposely placed in their way, even when their eyes were 

 put 'out or 'covered over, and hence thought that they must have 

 some other sense to direct them. It has been rendered probable, 

 however, that they owe this power to the delicacy of the sense of 

 touch in their wings and other parts. 



TASTE AND SMELL. 



The senses of taste and smell may be spoken of together, as they 

 appear in many places to be intimately connected. The sense of 

 taste resides in the tongue and mouth, and has generally been con- 

 sidered by physiologists as little more than a modification of touch. 

 The 5th nerve was supposed to confer both touch and taste. 

 Panizza, however, as was mentioned, has recently disputed this. 

 The papillae, already spoken of, are particularly well seen in the 

 tongue. If a fluid, such as strong vinegar, be applied with a hair 

 pencil, they will be seen to become curiously elongated. 



The tongue is covered with a thin cuticle, and the nostrils are 

 lined by a soft membrane, called, from a celebrated anatomist, the 

 Schn-eiderian membrane. It is upon this that the olfactory nerve 

 ramifies ; not, however, covered by it, but protected from the air that 

 passes through the nostrils merely by the natural secretion, called 

 mu-cus. The vapor of different bodies thus comes directly into 

 contact with these nerves. 



The following Figure shows the olfactory nerves which give the sense of smelling. 



Substances tasted must be either naturally fluid, or must be 

 dissolved by the saliva. When this condition is observed, we are 

 sensible of certain feelings, commonly supposed to be produced in 



