138 THE BOOK OF A NATURALIST 



when it is cautiously progressing through the 

 herbage, even when unalarmed, the tongue is 

 exserted at frequent intervals ; but I can say, 

 after a long experience of snakes, that the exserted 

 organ never touches earth, or rock, or leaf, or 

 anything whatsoever, consequently that it is not 

 a tactile organ. 



Another suggestion, less improbable on the face 

 of it than the one just cited, is that the tongue, 

 without touching anything, may, in some way not 

 yet known to us, serve as an organ of intelligence. 

 The serpent's senses are defective ; now when, in 

 the presence of a strange object or animal, the 

 creature protrudes its long slender tongue not to 

 feel the object, as has been shown does it not do 

 so to test the air, to catch an emanation from the 

 object which might in some unknown way convey 

 to the brain its character, whether animate or 

 inanimate, cold or warm blooded, bird, beast, or 

 reptile, also its size, etc. ? The structure of the 

 organ itself does not give support to this supposi- 

 tion ; it could not taste an emanation without some 

 such organs as are found in the wonderfully formed 

 antennae of insects, and with these it is not pro- 

 vided. 



Only by means of a sensitiveness to air waves 

 and vibrations from other living bodies near it, in 

 degree infinitely more delicate than that of the 

 bat's wing the so-called sixth sense of that animal 

 could the serpent's tongue serve as an organ of 

 intelligence. Here, again, the structure of the 



