We are indebted to Dr. Livingstone for much curious information respecting the serpents of South Africa, and especially in reference to the _Striking Echidna_, a singularly formidable viper, which the negroes designate _Picakolou_. He tells us that he killed one day a reptile of this species, which was of a deep brown colour, verging on black, and measured seven feet and a half in length.[128] These reptiles possess so abundant and deadly a venom, that when one of them is attacked by a band of dogs, the first dog bitten dies immediately; the second, five minutes afterwards; the third, at the end of an hour; and the fourth, after a more or less lengthened agony. A great number of beasts is annually destroyed by the Picakolous; the fangs of an individual killed at Kolobeng distilled poison for several hours after its head had been severed from its body. It is probably this plentiful secretion which the natives call "the serpent's spittle," and which leads them to suppose that the Picakolou is endowed with a power of injecting it into its enemies' eyes when the wind is favourable. [Illustration: Python Molure. Echidna, or _Picakolou_. Fennec (_Megalotis_).] Other venomous species exist in this part of Africa, of which several are vipers, and among others the Puff-Adder (_Vipera inflata_). The natives have named it _Noga-Poutsane_, or the Goats' Serpent, because it makes at night a bleating exactly resembling that animal. There were certainly no goats, says Livingstone, in the place where I happened to hear it. The natives suppose that by this bleating it hopes to deceive the traveller, and draw him within its reach. Some species emit, when they are frightened, a peculiar odour, strong enough to indicate their presence when they have found their way into the huts. There are also several varieties of Cobras (the _Naja-Haje_ of Dr. Smith). When they are attacked, they raise their head a foot from the ground, extend their neck in a threatening manner, dart their tongue to and fro with extreme rapidity, while rage glares in their fixed and glassy eyes. Different serpents of the genus _Dendrophis_, as, for example, the Green Climber (_Bucephalus viridis_), scale the trees in search of birds and their eggs, to which they are curiously partial. The Bucephalus is armed with fangs; nevertheless it is not venomous, and these fangs, which turn inwards, are only of use in preventing the retrogression of their prey, only one part of which is enclosed between its jaws.