The rattle is placed with the broad part perpendicular to the body, and not horizontal; and the first joint is fastened to the last vertebra of the tail by means of a thick muscle under it, as well as by the membranes which unite it to the skin; all the remaining joints are so many extraneous bodies, as it were, or perfectly unconnected to the tail by any other means than their curious insertions into each other.

The number of joints in the rattle of different individuals is very various, from five to twelve, fifteen, twenty, or even, according to some accounts, as many as forty. The pieces of which it consists are successively formed, each having been once attached to the muscle of the last vertebra of the tail, and driven on by the gradual formation of a young or immature one beneath it; but as it is not known whether these successive formations of new joints in the rattle correspond with the general changes of the skin, and as the part is also liable from its nature to occasional mutilations, it cannot be considered as a proper test of the animal's age.

The length of the individual dissected by Dr. Tyson, was four feet five inches; the girth of the body in the largest part six inches and a half; that of the neck three inches, and of the extremity of the tail, near the rattle, two inches.

[Catesby. Tyson. Grew. Phil. Trans. Shaw.

SECTION 1X.

Great Boa.

Boa constrictor.-LINN.

THE genus boa is remarkable for the vast and almost unlimited size of some of the principal species, which in India, Africa, and South America, are occasionally found of not less than twenty, thirty, and even thirty-five feet in length, and of a strength so prodigious as to be able to destroy cattle, deer, &c. by twisting around them in such a manner as to crush them to death by continued presure*, after which they will swallow them in a very gradual manner;

* This practice of larger serpents seems to have been well known to the ancients; thus Lucan, speaking of the monstrous African snakes, (which he also represents as furnished with wings,) tells us they destroy oxen, and even elephants, by writhing around and crushing them to death.

"Vos quoque, qui cunctis innoxia numina terris
Serpitis, aurato nitidi fulgore Dracones,

and when thus gorged with their prey, become almost torpid with repletion, and if discovered in this state, may without much difficulty be destroyed by shooting or other methods. There is reason to suppose, that these gigantic serpents are become less common now than some centuries backwards; and that in proportion as cultivation and population have increased, the larger species of noxious animals have been expelled from the haunts of mankind, and driven into more distant and uncultivated tracts: they are still however, occasionally seen, and sometimes approach the plantations and gardens of the districts nearest to their residence.

Of all the large Box the most conspicuous is the Boa Constrictor, which is at once pre-eminent from superiority of size and beauty of colours: in this respect indeed it appears to be subject to considerable variation from age, sex, and climate, but may be distinguished in every state from the rest of its tribe by the peculiar pattern or disposition of its variegations. The ground-colour of the whole animal, in the younger specimens, is a yellowish grey, and sometimes even a bright yellow, on which is disposed along the whole length of the back a series of large, chain-like, reddishbrown, and sometimes perfectly red variegations, leaving large open spaces of the ground colour at regular intervals: the largest or principal marks composing the chain-like pattern above-mentioned are of a squarish form, accompanied on their exterior sides by large triangular spots, with their points directed downwards; Pestiferos ardens facit Africa, ducitis altum Aera cum pennis, armentaque tota secuti Rumpitis ingentes amplexi verbere tauros.

Nec tutus spatio est Elephas; datis omnia leto;

Nec vobis opus est ad noxia fata veneno."

Ye too, in other climes who harmless rove

In gilded scales, the guardians of the grove,
In horrid Afric's pestilential air
Acquire new natures from the burning glare;
Ride thro' the blaze of noon on sable wing,
Quick on th' affrighted herds with fury spring;
And gathering all your folds in writhings dire,
Bid the huge ox beneath your crush expire;
Th' enormous elephant by force can slay,
And need no poison to secure your prey.

The tale of Laocoon, in Virgil, might be also adduced as an example of this particular.

between these larger marks are disposed many smaller ones of uncertain forms, and more or less numerous in different parts; the ground-colour itself is also scattered over by a great many small specks, of the same colour with the variegations; the exterior edges of all the larger spots and markings are commonly blackish, or of a much deeper cast than the middle part, and the ground colour immediately accompanying the outward edges of the spots is, on the contrary, lighter than on other parts, or even whitish, thus constituting a general richness of pattern, of which nothing but an actual view of a highly-coloured specimen of the animal itself can convey a complete idea. In larger specimens, the yellow tinge is often lost in an uniform grey cast, and the red tinge of the variegations sinks into a deep chesnut; and in some the general regularity of the pattern before described is disturbed by a kind of confluent appearance; the head is always marked above by a large longitudinal dark band, and by a narrower lateral band passing across the eyes towards the neck.

The boa constrictor is a native of Africa, India, the larger Indian islands, and South America, where it chiefly resides in the most retired situations in woody and marshy regions.

It was, in all probability, an enormous specimen of this very serpent that once diffused so violent a terror amongst the most valiant of mankind, and threw a whole Roman army into dismay. Historians relate this surprising event in terms of considerable luxuriance. Valerius Maximus thus mentions it from Livy, in one of the lost books of whose history it was related more at large.

"And since we are on the subject of uncommon phænomena, we may here mention the serpent so eloquently and accurately recorded by Livy; who says, that near the river Bagrada, in Africa, a snake was seen of so enormous a magnitude as to prevent the army of Attilus Regulus from the use of the river; and after snatching up several soldiers with his enormous mouth, and devouring them, and killing several more by striking and squeezing them with the spires of its tail, was at length destroyed by assailing it with all the force of military engines and showers of stones, after it had withstood the attack of their spears and darts: that it was regarded by the whole army as a more formidable enemy than even Carthage itself; and that the whole adjacent region being tainted with the pestilential effluvia proceeding from its remains, and the