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meet each other, continues gradually with the growth of the 

 tooth, forming first a half, and usually, at last, a complete canal. 

 This canal is the poison duct, and being thus formed, two results 

 ensue : — 1st. It is outside, and disconnected with the pulp- 

 cavily, but communicates with the tooth-follicle at its base. 2d. 

 It is only in the ivory substance, terminating, externally, at the 

 point where this last connects with the enamel ; the enamel 

 point being free and solid. 



Thus formed, these fangs seem to be in waiting to replace the 

 old ones in the event of their being removed, or naturally shed. 

 How this replacement takes place, I am unable to say from 

 observation. But it appears to me that the original tooth-follicle 

 becomes the poison-gland or sac ; for several of the larger re- 

 serve-fangs had each a small sac embracing its base, which 

 appeared to be only the primitive tooth-sac ; and, moreover, the 

 largest pair of these reserve fangs lay directly behind the ones 

 in use. The replacement might, therefore, occur as in the 

 •higher animals, — the pair of reserve passing gradually, together 

 with the poison-gland, into the places of those removed. 



But, however occurring, the substitution is exact and complete, 

 and may take place in a very short time, for Dr. Bearing in- 

 formed me, that from one of his captive specimens he extracted 

 the fangs, which were replaced in exactly six weeks ; this he 

 repeated several times with the same result. 



There are many facts tending to show that these fangs are 

 naturally shed once iix a while, if not regularly ; at all events 

 their points are likely to be broken off by frequent use, and, how- 

 ever removed, nature appears to have provided an ample stock 

 in reserve for their almost indefinite reproduction. 



The virulence of the poison of this animal is too well known 

 for special description. I will only add there is good reason for 

 the belief that its action is the same upon all living things, vege- 

 tables as well as animals. It is even just as fatal to the snake 

 itself, as to other animals ; for Dr. Dearing informed me that one 

 of his specimens, after being irritated and annoyed in its cage, in 

 moving suddenly accidentally struck one of its fangs into its own 

 body ; it soon rolled over and died as any other animal would 

 have done. Here, then, we have the remarkable, and, perhaps, 

 unique physiological fact, of a liquid secreted directly from the 



