Paraguay contains full twenty kinds of serpents, all differing in name, colour, size, form, and the nature of their poison. Those most commonly known are the Mboy̆tiñi, or Mboy̆chiñi, the Quiririò, the Yacaninà, the Mboy̆hobĭ, the Mboy̆quatia, the Mboy̆pe-guazù, or Cucurucù, the Mboy̆pe-mir̂i, the Yboyà, the Tarey̆mboyà, the Mboy̆guazù, or Yboyà, the Mboy̆roy̆, the Curiyù, the Ybibobocà, the Yacapecoayà, the Yararacà, the Cacaboyà, &c. The Mboy̆chiñi, or Rattle-snake, which is remarkable for its venom and the tinkling appendage to its tail, is about the thickness of a man's arm at the elbow, and often as much as five feet in length. It has a forked tongue, a flat head, little blackish eyes, four teeth in the upper jaw, besides other unusually acute and incurvated ones, from the hollows of which it darts poison at all it meets. Some lesser teeth are visible when the animal opens its mouth. The colour of the back, which is much deeper at the sides, is a dusky yellow, varied with yellow lines intersecting one another at the spine. It is covered with dusky scales, like those of a crocodile, but softer. The belly is of a yellowish colour, with rather large and almost parallelogram scales: at the extremity of the tail is situated that rattle from which it takes its name, and which is composed of a smooth, dry, cinereous material, the breadth of a man's thumb. Here and there it has a small hollow cell divided in the midst by a thin membrane, containing a little ball not perfectly round, which, being agitated by every motion of the serpent, and shaken against its receptacle, makes a sound like the wooden rattle which children use. Every year a fresh joint grows on to the rattle, as in stags-horns, connected with vertebræ, like the chains of a ring. From the joints of the rattle you may tell the age of the serpent, as you may that of a stag from the branches of his horns. Hence the older the serpent the more it rattles. This snake when angry coils itself up; when purposing an attack it moves along the ground so swiftly that it almost seems to fly. Providence has fastened that tinkling appendage to its tail in order to warn others from approaching it, for its poison is justly accounted the most virulent of any; the remedies which prove efficacious against the bites of other serpents, have been found unavailing against those of the rattle-snake, which causes certain but slow death, the deadly poison gradually diffusing itself through all the members. It takes away the use of the foot, arm, ear, and eye on that side which has been bitten, and presently, passing to the other, causes extreme torture, continual delirium, and acute pains, especially at the extremity of the feet and hands, which contract a cadaverous paleness from being deserted by the blood, which is rendered torpid by the coldness of the venom. All this I observed in two Guarany youths who were bitten by a rattle-snake. Both were under eighteen years of age,