CLASS III. REPTILIA: ORDER 4. OPHIDIA. 387 
locomotion : they can creep, glide, grasp, suspend themselves, erect themselves, leap, dart, 
hound, swim, and dive. They are mostly oviparous, their eggs being soft, of a yellowish-white 
color, covered with a leathery skin, and from twenty to thirty in number at each laying. 
Their senses ai'e not very acute ; the eyes are small, and without lids ; the tongue is free, forked, 
and capable of considerable elongation and rapid motion. They are divided by Dr. Gray into 
two sub-orders, the Viperina, or Venomous Seijoents^ and the Colubrina, or Coluhrine Snakes, 
which are for the most part harmless, though some of them are otherwise. These animals are 
exceedingly numerous, no less than one hundred and fifty species being in the Catalogue of the 
British Museum. We shall only attempt to describe a few of the most remarkable kinds. 
THE YIPERmA. 
The Viperina, so far as known, are all ovo-viviparous ; they are also distinguished by the pecu- 
liar arrangement of the teeth in the upper jaw. The true maxillary bones are reduced to a very 
small size, capable of a great amount 
of motion, and bear a single pair of long 
curved fangs, which can be laid flat in 
the mouth during repose, or erected 
when in action by the agency of pecu- 
liar muscles. These are the only teeth 
supported by the maxillary bones ; 
they are perforated throughout by a 
slender canal, which communicates with 
a large gland situated in the head, be- 
hind and under the eyes. This secretes 
the venomous fluid, which passes through 
a duct to the base of the tooth, and 
thence through the canal in its interior, 
until it is injected into the wound made 
by the bite of the serpent. Its propulsion is efl'ected partly by the contraction of the proper walls 
of the gland, and partly by the pressure of the muscles of the jaws, which act upon it during their 
contraction. The poison which is thus injected into the wound mixes with the blood, and is then 
carried into the circulation, where it speedily produces an injurious effect, giving rise to an altered 
condition of the blood, which, if the poison be present in sufiicient quantity, quickly renders it 
incapable of supporting life. In fact, a bite from one of the large poisonous snakes of tropical 
chmates is generally fatal, even to man, if the animal be in a vigorous condition, and provided 
with a good supply of poison ; but a bite from a similar snake, after it has nearly exhausted its 
venom hj previous attacks, may give rise to little or no inconvenience. It is remarkable, also, 
that the eff'ect of the poison of these creatures is very difi"erent upon different animals ; the cold- 
blooded species in general appear to be almost indifferent to its effects, while most warm-blooded 
animals soon expire when a sufiicient quantity is injected into their veins. Various means of 
preventing the injurious effects of the bite of these reptiles have been proposed, and the natives 
of most countries in which they abound have their favorite antidotes for the wounds inflicted by 
them. The only means, however, upon which it appears that much reliance can be placed, are 
SECTION OF THE HEAD OF A SEEPENT. 
a, poison fangs ; i, poison glands ; c, conductor for the poison ; d d, 
muscles of the jaws; e, tendon of the muscles; s, salivary glands. 
