It does not follow from this that the bites of these reptiles are less dangerous; the contrary, indeed, is the case, for their venom is infinitely more active. These differences, as well as the particular mode of arrangement of the other little non-poisonous teeth in both jaws, enable us in many cases to recognise, by the mere appearance of the bite, the species of snake by which the bite has been inflicted. [Illustration: FIG. 7.--MARKS PRODUCED ON THE SKIN BY THE BITES OF DIFFERENT SPECIES OF SNAKES. I. _Non-venomous Colubrine._--The bite is marked only by the imprint of from 35-40 small palatine or pterygoid teeth, and 20-22 upper maxillary teeth (on the outside of the foregoing) on each side. II. _Venomous Colubrine_ (_Naja tripudians_, PROTEROGLYPHA).--The bite exhibits 25 or 26 punctures from the pterygoid or palatine teeth, and, on each side, one or two, rarely three, circular wounds produced by the principal poison-fangs and by the reserve teeth. 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. [Illustration: 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.)] In a few venomous snakes the gland is developed to such an extent that it extends as far as the first ribs. The species, on the contrary, that have the poison-teeth placed in the hinder part of the mouth (_Opisthoglypha_) have glands but little developed. * * * * *