The exceptions to this rule are, however, too numerous for its value as a
distinguishing character in a question of such practical moment as the
venomous or non-venomous properties of a serpent. In all the fam ily
of marine serpents the poison-fang is only the foremost of a row of
fixed maxillary teeth : in the Hydrophis striatus (PI. 65, fig. 14) there
are four teeth, and in Hydrophis schistosa (fig. 15) five teeth, behind
the venom-fang, of rather smaller size than it ; the two-coloured sea-
snake (Pelamys Ucolor) has also five maxillary teeth in addition to
the perforated one. The poison-fang, in this genus, is relatively
smaller than in the venomous serpents of the land, hut presents the
same peculiar structure. The poison-gland presents a correspondingly
small development ; it is pyriform, and its structure,
according to Dr. Canter(l), is minutely cellular; it is covered
by the aponeurotic expansion of the articulo-maxillaris (PL 65,
fig. 15, e, f), and transmits a straight duct horizontally to the
basal opening of the venom-fang. It is a curious fact that the
smaller non-venomous teeth of the poisonous serpents all present a
trace of the structure of the functional venom-fang, being more or
less deeply grooved along the convex anterior side ;(2) and in the
Hydrus this groove commences by a depression analogous to the
oblique basal aperture of the poison-canal in the true fang.
The colubriform poisonous serpents of the land have comparatively
short venom-fangs, but they are larger than those of the pelagic serpents;
and behind the venom-fangs there are likewise some smaller grooved
teeth in the maxillary bones : there are three such teeth in the Bunga-
rus Pama, and five in the Bungarus annulatus. In the Humadryas or
great hooded poisonous tree-snake of India, the venom-fang is relatively
as large as in typical poisonous serpents, but three or four
smaller grooved teeth are implanted behind it on the maxillary
bone.
In the most deadly venom-snakes, as the viper (Berm), the puffmaxillary,
and c d the palato-pterygoid series of teeth in both species. In the Naja the maxil-
lary senes is reduced to a single fang. •
(1) Zool. Transactions, vol. ii, p. 304.
(2) The presence of similar grooved teeth in Serpents which are not armed with venom-
angs has already been noticed : such teeth are never found in the Boas and Pythons.
adder (Vipera), the asps or hooded-snakes (.Naja), the rattle-snakes
(Crotalus), the cophias and fer-de-lance (Trigonocephalus), the poison
fangs acquire their largest size, and are associated only with their
successors : these are clustered in greater or less number behind them,
presenting the same structure, but of a size proportionate to their degree
of development, and further differing in being loosely imbedded in the
thick and wide mucous gum, which likewise conceals the fixed and
functional fang in its ordinary position of retraction and repose. This
fang is more strongly curved backwards than the ordinary teeth,
but its acute and slender apex is frequently bent slightly in the contrary
direction, as in the rattle-snake, (PI. 65, fig. 8, b).
The mechanism by which the short maxillary bone and the
poison-fang are rotated backwards and forwards upon the ginglymoid
joint that connects the maxillary with the prefrontal and palatine
bones has already been noticed, and, as some description of the
secreting apparatus to which the peculiar modification of the venom,
fang is subservient might here be expected, I have selected for its
illustration the accurate figure which Prof. Muller has given of the
salivary and poison-glands in the Trigonocephalus lanceolatus in his
great work on the Glandular System.(l)
The poison-glands (PI. 65, fig. 12, a) occupy the sides of the posterior
half of the head; each consists of a number of elongated narrow lobes,
extending from the main duct which runs along the lower border of the
gland, a, upwards and slightly backwards : each lobe gives off lobules
throughout its extent, thus presenting a pinnatified structure ; and each
lobule is subdivided into smaller secerning caeca, which constitute
the ultimate structure of the gland. The whole gland is surrounded
by a double aponeurotic capsule, b, b, of which the outermost and
strongest layer is in connection with the muscles by whose contraction
the several caeca and lobes of the gland are compressed and emptied of
their secretion. This is then conveyed by the duct, c, in the course
of the dotted line, e, to the basal aperture of the poison-canal of the
fang. We may suppose, that as the analogous lachrymal and salivary
glands in other animals are most active during particular emotions, so
the rage which stimulates the venom-snake to use its deadly weapon
(1) De Glandularum Secernentium Structure Penitiori, fol. tab. vi, fig. 1, p. 55.