166 



THE VITAL FUNCTIONS. 



growth. Fig. 292 is a section of a full-grown 

 fang of the same species of serpent, at the same 

 part as the preceding ; and here the cavity of 

 the pulp is seen much contracted from the more 

 advanced stage of growth. 



It is a remarkable circumstance, noticed by 

 Mr. Smith, that a similar longitudinal furrow 

 is perceptible on every one of the teeth of the 

 same serpent ; and that this appearance is most 

 marked on those which are nearest to the 

 poisonous fangs : these furrows, however, in the 

 teeth that are not venomous, are confined en- 

 tirely 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 are 

 converted to uses widely different from mastica* 

 tion, may be noticed that of the Squalus pristis. 



or Saw-fish, where the teeth are set horizontally 



