III. Viperidæ (Solenoglypha).—The sole indication of the bite consists of 8 or 10 punctures from the palatine or pterygoid teeth, and one little round wound, on each side, produced by the poison-fangs.
(After Sir Joseph Fayrer.)
Fig. 7, above, shows how it is possible to distinguish the marks left by a non-venomous reptile, and by one of the Proteroglypha or Solenoglypha respectively.
Poison-glands.—The poison-glands occupy an extensive inter-muscular space behind the eyes, on each side of the upper jaw. They are oval in shape, and may, in Naja tripudians for example, attain the size of a large almond ([fig. 8]).
Their structure is the same as that of the salivary glands of the larger animals. The poison that they secrete accumulates in their acini and in the efferent duct that opens at the base of the corresponding fang.
Each gland is surrounded by a capsule, to which are partly attached the fibres of the masseter muscle, which violently compresses it and drives the poison, just as the piston of a syringe would do, into the canaliculi or groove of the fang.
Fig. 8.—Poison-gland and Fangs of a Venomous Snake (Naja tripudians, Colubridæ). (Natural size.)
L, Lobe of the gland; D, poison-duct; F, fang attached to the maxillary bone; G G, gland; M, capsule of mucous membrane surrounding the fangs; R, reserve fangs; A A, muscular fascia covering the gland.
(After Sir Joseph Fayrer.)