/f6 
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Bis 
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x = 
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Fic. 139.—A. Section of a Viperine Fang. 1. Canal through which the venomruns. 2. The 
central pulp of the tooth. B. Section of a Colubrine Fang. 1. Groove down which the 
venom runs. 2. Central pulp of the tooth. C. Fang of a Viperine Snake. 1. Hole 
through which the venom enters the canal. The end of the duct from the poison gland is 
connected with this hole. 2. The outlet of the hole near the end of the fang through 
which the venom escapes. The outlet is oblique, and is not at the extreme tip of the fang. 
3. The direction of the canal through the tooth. 1a. Skull of a Viperine Snake, showing 
the position of the bones, muscles, and fang when the mouth is closed. rb. A diagram 
showing principle how the fang is worked. In this figure the fang is depressed to 
represent the mouth closing. 11a and rrb, Position of the apparatus when the mouth 
is opened widely ; the spheno-pterygoid muscle (Pe) is contracted: the Pterygoid (Pt) 
is pulled forwards, the transverse bone or Ectopterygoid (Tr) pushes the Maxillary (M) 
rotates it, and thereby causes the Poison Fang (J) to assume an erect position. (Di) 
Digastric Muscle, contraction of which lowers, or opens the lower jaw. (J) Poison Fang, 
(M) Maxillary, (P) Palatine, (Pe) Spheno-pterygoid Muscle, (Pm) Pre-maxillary, (Pt) 
Pterygoid, (Q) Quadrate, (Sq) Squamosal, (Ta) Insertion of the anterior temporal muscle, 
by contraction of which the mouth is shut. D. The whole poison apparatus of a Viperine 
Snake. 1, Articular-maxillary ligament. 2, 3, and 4. Temporal Muscles. 5 and 6, 
Constrictor Muscles of Poison Gland. 7. Duct. 8. Outlet of Duct. This is the point 
where the venom enters the canal in the fang. 9. Maxillary Bone. ro. The canal 
through the fang. No. 5 and 6 are the Constrictor Muscles which wring the poison gland, 
and cause its contents to run along the duct into the hollow fang. The mechanism of 
Colubrine snakes is the same, excepting that their fangs are usually grooved, instead of 
being hollow. 
2A 
