Schlegel describes the forms which the bodies of various snakes assume in swimming, climbing, clinging, etc. Sometimes they are laterally compressed, at others flattened. The three figures above are on a much reduced scale, but give an idea of the sections of three different snakes, though each snake is capable of several such changes of form. When snakes climb against the glass of their cages, you may easily discern the flattening of their bodies. In this action there seems to be a compressing power, any hold of the scutæ against a polished plane being, of course, impossible; yet without holding they seem to cling; and the ribs advance in wave-like intervals just the same, with an intermediate space at rest until in turn the wave is there and passes on, while from an anterior portion another wave approaches, and so on. Yet the compressure strikes one forcibly. There is also the evident support of the tail in a large python thus crawling to the very top of his cage.
Mr. Gosse observed the dilatation and flattening of the body in the climbing snakes, and that they had no more difficulty in gliding up a tree or a wall in a straight line than on the ground. In the Anecdotes of Serpents, revised for the Messrs. W. & R. Chambers, of Edinburgh, in 1875, from the tract by the late John Keast Lord, I also recorded my observations on this peculiarity.
Some young Jamaica boas crawled to the top of their cage as soon as they were born. I saw them the same day; held them, as well as it was possible to hold threads of quicksilver; felt them, too, for the exceedingly juvenile constrictors tied up my fingers cleverly. So did some young boa constrictors, born alive at the Gardens, June 30, 1877. They were from fifteen to twenty inches in length, and had teeth sufficiently developed to draw blood from Holland’s hand, showing fight and ingratitude at the same time. They were exceedingly active, and fed on young mice, which they constricted instinctively. One of them, known as ‘Totsey,’ subsequently hung for her portrait, as on p. 201.
In vol. xx. of Nature, p. 528, is a very clever paper on the progression of snakes, by H. F. Hutchinson, who has evidently observed them closely. He arrives at the conclusion that they have three different modes, viz. ‘on smooth plane surfaces by means of their rib-legs;’ ... ‘through high grass by rapid, almost invisible, sinuous onward movement, like swimming;’ in climbing straight walls or ascending smooth surfaces by creating a vacuum with the ventral scales. He reminds us that cobras, kraits, the rat snake, and other slender and active kinds are constantly found on house roofs, walls, straight smooth trees, etc., and asks how they got there. He has seen the ‘abdominal scales creating a vacuum like the pedal scales of house lizards.’ He put some active little snakes on the ground, where there was no hold for the scutæ, and they ‘flew about in all directions.’ He saw that they moved on by these quick, sinuous curves—‘rapid wriggles.’
In company with my esteemed friend, Mr. Robert Chambers of Edinburgh, we made similar experiments by placing some of the smooth-scaled, active snakes on a boarded floor. Being extremely wild, they displayed their anger and skill to perfection, and literally swam along, scarcely touching the floor, and so swiftly that we had difficulty in pursuing and securing them again. Some very young Tropidonoti when disturbed flew or ‘swam’ about their cage in the same manner. We also saw pythons climb up a window-frame, and a corner of the room where no visible hold could be obtained; and after the example of Sir Everard Home, we allowed the reptiles to crawl over our hands, when we could feel the expansion and flattening of the body by the spreading of the ribs. I incline to agree, therefore, with the writer in Nature, that there is a sort of vacuum created by the ventral scales. Dr. Stradling observed that on occasions of retreat, some snakes move in such rapid and ever-varying sinuations as to baffle you completely when you attempt to lay hold of them; the part you thought to grasp is gone.[69] Such are the movements of Pituophis and of Echis (p. 151).
At the risk of being tedious, a few more words must be added on this subject of progression, because we so constantly see it asserted that snakes ‘move with difficulty over smooth surfaces.’ Their actions have not excited sufficient attention and study. Have you ever watched them moving about in their bath at the Zoological Gardens? The motions of a python once particularly struck me. The earthenware pan was smooth polished ware, and with enough water in it to render it smoother, if that be possible. The reptile was not swimming, for the thicker part of its body was not even wholly submersed. The pan was too shallow for that, and too small to permit of any portion of the python being fully extended. It moved in ever-varying coils and curves, yet with the greatest ease, its head slightly raised, so that the nostrils and mouth were out of water. It seemed to be enjoying its bath, as it actively glided, turned, and curved in that wonderful fashion which Ruskin described as ‘a bit one way, a bit another, and some of him not at all.’ There could be no hold for the scutæ in this case, nor could I detect any action of the ribs as in crawling over a less smooth surface. The creature seemed to move by its easy sinuations, and with no more effort than you see in the fish at an aquarium. Perfectly incomprehensible is this lax and leisurely movement in shallow water. Even the inert little slow-worm astonishes us by its physical achievements, which will be duly described in its especial chapter.
But among the most characteristically active are the small and slender tree snakes, the Dryadidæ and Dendrophidæ, mostly of a brilliant green. These and the Whip snakes are exceedingly long and slender, the tails of many of them very gradually diminishing to a fine and attenuated point. Some of them are closely allied to the lizards, and skim and dash through the foliage with a scarcely perceptible weight. These are the true acrobats, full of gracile ease and activity. Many are over four feet in length, and not much thicker than a pencil.
They are found in the hot countries of both hemispheres. The Siamese call some of them ‘sunbeams,’ from their combination of grace and splendour, and in Brazil some have the brilliant tints of the humming-birds. These little creatures in your hand feel like soft, fine, satin cords endowed with life.
Dr. Wucherer, writing from Brazil, enthusiastically declared that he was always delighted to find one of them in his garden. He discovered them coiled in a bird’s nest, their body of two feet long occupying a space no larger than the hollow of your hand. ‘In an instant they dart upwards between the branches and over the leaves, which scarcely bend beneath their weight. A moment more, and you have lost them.’[70]
Krefft, of Australia, had some of the active snakes, which were confined in an empty room, but one day could not be found. At last they were discovered upon the moulding of a door, nine feet from the floor! They must have climbed up the smooth wood-work in their own mysterious fashion.