164 
RECEPTION OF SOLID AND LIQUID ALIMENT. 
of Insects, of which a pair is attached to each jaw (fig. 84); 
the tentacula of Mollusks, which are sometimes extremely 
prolonged, as in the Cuttle-fish tribe (fig. 85) ; and the 
similar organs of the polypes (fig. 71). 
173. The reception of liquids is accomplished in two ways. 
Sometimes the liquid is made to fall into the mouth, simply 
by its own weight (fig. 86); in other instances it is drawn or 
pumped up into this cavity,—either by the expansion of the 
chest, which causes a rush of air towards the lungs,—or by 
the movement of the tongue, which, being drawn back like a 
piston, produces the action of sucking. Some of the lower 
animals are destined to be entirely supported by liquids which 
they find in plants, or which they draw from the bodies of 
other animals whereon they live as parasites. This is the 
case with many Insects ; and their mouth, instead of present¬ 
ing the ordinary structure, is formed into a sort of tube or 
trunk, very much extended, through which the juices are 
drawn up according to the wants of the animal. Such a 
conformation exists in the butterfly and moth tribe, whose 
