Of the practical uses of the snake’s tail, the _natural_ uses,—those above mentioned being either imaginary ones, or a mere expression of feeling,—the prehensile power is one of the greatest. ‘Strictly speaking, the true prehensile tail is found only in the boa,’ Schlegel, Owen, and other physiologists tell us; but that statement refers to some peculiar anatomical construction, enabling the tail to twine and grasp with extraordinary force, because nearly all snakes can manage to climb, or to raise themselves when occasion requires it, making use of their tails, as was stated at the commencement of this chapter. ‘Even the clumsy, ugly death adder can climb well,’ Krefft assures us, and that it can support itself against a wall with only a portion of its tail on the ground. Many writers and observers, in describing this power or force in the snake, have given rise to the idea that snakes can _stand_ on their tails. Erect themselves nearly upright they certainly do, even without extraneous support for a few moments, and _with_ support for a considerable time. Cobras can do this. A personal friend, Colonel C——, when in India, once heard a sort of muffled sound at his door, which caused him to open it suddenly, when a cobra, which had raised itself three or more feet against it, fell straight into the room. He sprang quickly aside, and ran to fetch a stick, but when he got back the cobra was gone. But to return to their prehensile powers. Snakes which are not habitual climbers are often found in trees, suspending themselves from or supporting themselves upon the branches, as instanced in the chapter on the egg-eaters. The _Hamadryad_ is also much in trees, as its name implies, and is seen hanging from the branches. This latter, and also the Indian tree snakes, _Trimeresuri_, are poisonous, and far removed from the boas with the true prehensile tail. Familiar to every one are illustrations of tropical scenery, in which the boa constrictor and the anaconda, hanging from trees, are important features. Dumeril, in general terms, says: ‘Les ophidiens rampent, glissent, s’accrochent, se suspendent, gravissent en s’aidant de la totalité de leur corps, sautent, s’élancent, bondissent, nagent, et plongent,’[56] in every one of which movements the tail is an important agent. _S’accrocher_ and _se suspendre_ must be mainly by the agency of the tail. Schlegel follows up his statement, ‘tail strictly prehensile found only in boas,’ by explaining, nevertheless, that a short tail is sufficiently vigorous to _attach_ itself to any point, and support the whole body.[57] In the non-venomous tree snakes the tail is long and slender, and no squirrel or bird is more active and at home in a tree than these. They glide, swing, climb, and almost fly from branch to branch, scarcely disturbing a leaf.