REPTILES. 283 



The armature of the mouth is of two kinds, common 

 teeth, and poison fangs. The common teeth form a single 

 row on each side in the lower jaw, and usually a double 

 row in the upper. The external row, above, is connected 

 with the maxillary bone ; the inner row is supported, as in 

 many fishes, on the palatine bones. These teeth are subu- 

 late and recurved. 



The poison fangs, vulgarly termed the sting, are confined 

 to the upper jaw, and occur on each side towards the ex- 

 tremity. In some, the fang is the largest tooth, the fore- 

 most in the row, and is followed by several common teeth 

 in the maxillary bone. In others, the maxillary bone is 

 abbreviated, and the deficiency at its proximal end is sup- 

 plied by a long moveable peduncle destitute of teeth. The 

 large fang is placed in this short maxillary bone, and is 

 followed by a few other teeth of similar form. These fangs 

 are to be viewed as the osseous openings of the ducts from 

 the poison-bags, which are situate at the base. They 

 contain a tubular cavity from their base, passing through 

 the tooth on its convex side, to the apex, where it ends 

 in a narrow slit. When the serpent bites an animal, the 

 poison flows from the bag through this slit, into the bottom 

 of the wound, where, to most advantage, it can produce its 

 deleterious effects. Whether this dreadful apparatus of 

 venom is to be considered as connected with the digestive 

 system, as an instrument for conquering the prey, and ob- 

 taining food, or for defensive purposes, has not been satis- 

 factorily determined. The latter conjecture is the most 

 plausible. 



The true structure and mode of formation of the poison 

 fangs, appear to have been first investigated with care by 

 Mr SMITH. He found that the poison tube was formed by 

 a fold on the surface, the edges of which met in the mid- 



