88 THE VITAL FUNCTIONS. 



lancets.* In the gnat, they are five or six in number, finer 

 than a hair, exceedingly sharp, and generally barbed on one 

 side. In the Tabanus, or horse-fly, they are flat like the 

 blade of a knife. These instruments are sometimes con- 

 structed so as to form, by their union, a tube adapted for 

 suction. In the flesh-fly, the proboscis is folded like the 

 letter Z, the upper angle pointing to the breast, and the 

 lower one to the mo^uth. In other flies there is a single 

 fold only. 



Those insects of the order Hymenoptera } which, like the 

 bee, suck the honey of flowers, have, together with regular 

 jaws, a proboscis formed by the prolongation of the lower 

 lip, which is folded so as to constitute a tube: this tube is 

 protected by the mandibles: and is projected forwards by 

 being carried on a pedicle, which can be folded back when 

 the tube is not in use. The mouths of the Acephalous Mol- 

 lusca are merely sucking apertures, with folds like lips, and 

 without either jaws, tongue, or teeth, but having often ten- 

 tacula arising from their margins. 



Among fishes, we meet with the family of Cyclostomata, 

 so called from their having a circular mouth, formed for 

 suction. The margin of this mouth is supported by a ring 

 of cartilage, and is furnished with appropriate muscles for 

 producing adhesion to the surfaces to which it is applied; 

 the mechanism and mode of its attachment being similar to 

 that of the leech. To this family belong the Myxine and 

 the Lamprey. So great is the force of adhesion exerted by 

 this sucking apparatus, that a lamprey has been raised out 

 of the water with a stone, weighing ten or twelve pounds, 

 adhering to its mouth. 



Humming birds have a long and slender tongue, which 

 can assume the tubular form, like that of the butterfly or the 

 bee, and for a similar purpose, namely, spcking the juices of 

 flowers. Among the mammalia, the Vampire Bat affords 

 another instance of suction by means of the tongue, which 



* Kirby and Spence's Entomology, vol. iii. p. 467. 



