350 ANNUAL OF SCIENTIFIC DISCOVERY. 



structure of the enamel. This enamel is formed very early, and some- 

 time before the appearance of the dentine or ivory ; so that at one 

 period you find simply the epithelial tooth-sac crowned with a point of 

 enamel. As the tooth-sac increases and is pushed out, the enamel 

 point is more and more elongated, becoming finally very long and 

 acicular, and with the sharpness well known in the perfect fang. 



Meanwhile the dentine, or ivory, is formed, and as this process is 

 going on, its edges begin to roll towards each other on the convex and 

 upper surface of the tooth. This rolling of the edges to meet each 

 other, continues gradually with the growth of the tooth ; being 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-cavity, 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, therefore, being free and solid. 



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



O ~ 1 



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 reserve-fangs had each a small sac, 

 embracing its base, and 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 

 with 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. Dearing informed me, 

 that from one of his captive specimens, he extracted the fangs which 

 were exactly replaced in six weeks ; this he repeated several times 

 with a like result. 



There are many facts tending to show that these fangs are naturally 

 shed once in a while -if not regularly ; at all events, their points are 

 likely to be broken off by frequent use, and however removed, Nature 

 appears to have provided an ample stock in reserve for their almost 

 indefinite repletion. 



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

 special description. I will only add there is good reason tor the belief 

 that its action is the same upon all living things, vegetables 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 blood, which proves deadly when introduced into the 

 very source (the blood) from which it was derived ! 



With the view of ascertaining the power and amount of this poison, 

 Dr. Dearing performed the following experiment ; the snake was a 



