412 



ANATOMY OF VERTEBRATES. 



tissue. But the surface of the prominent tongue is generally 

 callous,, and either smooth and devoid of papillae, or, if the repre- 



277 



Vertical section of mouth, Lamprey, v. 



sentatives of these be present, they are calcified and the tongue is 

 beset with teeth. It, then, seizes and passes the food on to the 

 gullet; but the supporting arch of the tongue, fig. 85, 38-40, works 

 chiefly for respiratory purposes. In the Lamprey, the tongue, fig. 

 277, d, is more exclusively related to the digestive function than 

 in higher Fishes : it can be protruded and retracted, like a piston, 

 when the sucker is attached to the prey ; and it is armed by small 

 serrate teeth for tearing the flesh. In a few Fishes the integu- 

 ment of the palate presents that degree of vascularity and supply 

 of nerves which indicates some selective sense, analogous to taste. 

 In the Cyprinoids the palate is cushioned with a thick soft 

 vascular substance, exuding mucus by numerous minute pores, 

 but more remarkable for its irritable erectile or contractile 

 property : l if any part of this be pricked in a live Carp, the part 

 rises immediately into a cone, which slowly subsides ; this peculiar 

 tissue is richly supplied by branches of the glosso-pharyngeal 

 nerves : it may assist in the requisite movements of the vegetable 

 food, as well as add to it an animalising and solvent mucus, whilst 

 it is undergoing mastication by the pharyngeal teeth. In the 

 Gymnotus there are four series of branched fleshy processes in the 

 mouth, one upon the dorsum of the tongue, a second depending 

 from the palate, and one along each side of the mouth. 



The only representatives of a salivary system in Fishes are the 

 mucous follicles that communicate with the mouth. 2 The chief of 



1 XCIX. 



2 The reddish vascular body, discovered by Retzius (cxxi.) between the basi- 



