NATURAL HISTORY OF SELBORNE. 
445 
be seen that it envelops more than one poison fang. Tliere 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 o(f or is shed, another imme- 
diately conies 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 
suture of the inflected margins runs along the FANGS 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 hite. 
It rather gives a sharp instantaneous stab, knowing instinctively 
that 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. AVhen 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 
