ORGANS OF DIGESTION. 379 



canal is shorter than the intestinal portion beyond the 

 stomach, and numerous complicated salivary glands, which 

 pour their secretions into the mouth, are rarely deficient 

 in these classes. The chyle is now conveyed into the blood 

 by a distinct system of chyliferous vessels. There are no 

 gastric teeth, nor transverse maxillae, and the atlantal ex- 

 tremities often assist in the prehension and division of the 

 food. The jaws move in a longitudinal direction, and the 

 teeth, when present, are confined to the buccal cavity, and 

 most commonly the alveolar margins of the jaws. The 

 differences presented by the digestive organs in the ver- 

 tebrated classes relate chiefly to the nutritious quality, the 

 consistence, and other properties of the food, and to the 

 degree of development in the general organization of the 

 body. The alimentary canal becomes more elongated, and 

 the chylopoietic glands more complicated by the ramifications 

 of their tubuli, as we ascend through the classes ; but the 

 canal is proportionably most elongated, capacious, and sac- 

 culated, in the phytophagous tribes, where the glands are 

 also most developed, and the development and solidity of 

 the masticating organs are proportioned to the resistance 

 of the food and the mechanical division it requires to undergo 

 in the mouth. 



XIX. Pisces. As fishes are mostly predaceous animals 

 which swallow their prey entire, their oesophagus is short 

 and wide, their stomach capacious, and their intestine short ; 

 their chylopoietic glands are moderately developed, and their 

 teeth are generally in form of prehensile organs little adapted 

 for mastication. The exterior of the mouth is sometimes 

 provided with fleshy tentacular developments, like those 

 of mollusca, as in the Lophius, Antennarius, Batrachus, and 

 Cobitis, and the prehensile oral disk of many of the cyclos- 

 tome fishes is furnished with sharp conical curved spines, 

 like the arms of the onychia among the cephalopods. The 

 dermal nature of teeth is most obvious in the fishes, where 

 they develope successively and repeatedly during life from 

 their cutaneous pulps over all parts of the mouth, like solid 

 sheaths of cutaneous papillae, and they are often arranged in a 

 quincunx order, like hairs and feathers ; they are mere osseous 

 crowns of teeth, thinly covered with enamel, destitute of fangs, 

 laminated, deciduous, and moveable on the surface of the 



