1388 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 
