122 



THE VITAL FUNCTIONS. 



of the pulp is seen much contracted from tlie more advanced 

 staf];e of growth. 



It is a remarka])le circumstance, noticed by Mr. Smith, 

 that a similar lonii;itudinal furrow is perceptible on every- 

 one of the teeth of the same serpent; and that this appear- 

 ance is most marked on those which are nearest to the poi- 

 sonous fangs: these furrows, however, in the teeth that are 

 not venomous, are confmed entirely to the surface, and do 

 not influence the form of the internal cavity. No trace of 

 these furrows is discernible in the teeth of those serpents 

 which are not armed with venomous fangs. 



Among the many instances in which teeth arc converted 

 to uses widely different from mastication, may be noticed 

 that of the Squalus pristis, or Saw-fish, where the teeth are 

 set horizontally on the two lateral edges of the upper jaw, 

 which is prolonged in the form of a snout (seen in a, Fig. 

 293,) constituting a most formidable weapon of offence, b 



is a more enlarged view of a portion of this instrument, seen 

 from the under side. 



§. 5. Tr 'duration of Food in Internal Cavities. 



The mechanical apparatus, provided for triturating the 

 harder kinds of food, does not belong exclusively to the 



