NATURAL HISTORY OF SELBORNE. 137 



lie, seen that it envelops more than one poison fang. There are 

 generally five or six in a row, one after the other. On each side 

 of the snake's mouth one fang is fixed firmly on to the bone 

 which works it ; the others are all more or less loose, and by 

 some wonderful process, not yet known to us men, when the 

 front fixed tooth gets broken off or is shed, another imme- 

 diately comes up as its successor from behind. It will be 

 observed that there is a small bristle running through the largest 

 of the fangs, the tooth in fact is perforated by a beautiful duct 

 or pipe. 



Professor Owen thus writes in his valuable work "Odontography : 

 or, A Treatise on the Comparative Anatomy of the Teeth " : " A 

 true idea of the structure of a poison-fang will 

 be found by supposing the crown of a simple 

 tooth, as that of a Boa, to be pressed flat and its 

 edges to be then bent towards each other, and 

 soldered together so as to form a hollow cylin- 

 der open at both ends. The flattening of the 

 fang and its inflection around the poison-duct 

 commences immediately above the base, and the 



,. . n . i Fio. 2. -POISON 



suture of the inflected margins runs along the FANOS DISSECTED. 

 anterior and convex side of the recurved fang. 

 The poison canal is then in front of the pulp cavity." When a 

 poisonous snake strikes its enemy, it can hardly be said to lite. 

 It rather gives a sharp instantaneous stab, knowing instinctively 

 Unit the poison once injected into the wound will do its work. 

 To enable them to strike so quickly, all poisonous snakes have, 

 about the foremost few inches of their body, very great powers 

 of darting. 



When experimenting on the poison of living vipers, I found 

 that, when a viper is held tight by the neck, he will erect his 

 two working fangs and move them backward and forward with 

 more or less rapidity, exactly as a man moves his arms when 

 about to fight another. When the viper was thoroughly enraged 

 and had got his steam up, I placed quickly a microscope slide 

 under the fangs. In one moment the fangs came sharply down 

 upon the glass and two drops of poison were emitted, one from 

 each fang. I instantly put these under the microscope, and 

 witnessed a most extraordinary appearance, namely, a crystalliza- 

 tion of the poison. I have not space to describe this in detail 

 suffice it to say that the poison, when nearly evaporated very 

 much resembled the crystals of hoar frost on window panes on 

 frosty mornings. This, I believe, has not been observed for 

 about a hundred years ; by great good luck I discovered that Dr. 

 Mead both saw and described it This learned doctor's account 

 VOL. II. T 



