Bones, are solid substances composed of animal earth and gluten. They support and form the stature of the body, defend its viscera, and give adhesion to the mus-cles. Their number in the human frame is generally 240; but jn some individuals, who have two additional bones in each thumb and great toe they amount to 248. The regular division of them is as follows : 03 bones of the head, including the 32 teeth; 53 of the trunk 64 of the upper, and 60 of the lower extremities.

One of the most remarkable diseases of animal bones, is their occasional softness and reduction in the living body; of which there are several well-authenticated instances. The late Mr. Gooch, a respectable surgeon of London, relates the case or" a woman naturally live feet six inches high, who was gradually reduced to three feet four inches. In rickety children, the bones are obviously softer than they ought to be in a sound state, owing, perhaps, to their erosion, occasioned by the discharge of an acrimonious humour. In a similar manner, the scurvy has often been remarked to affect these solid parts of the human frame. Hence, in the former instances, attention to a proper diet, gentle friction with coarse cloths, exercise, fresh air, and cold bathing, will frequently change the constitution of such children, insomuch, that at the age of twenty there will not remain the least symptom of their former debility.

It is generally believed, that the bones, in a healthy state, are in" sensible to pain, because the larger ones are unconnected with any nerve : hence the operation of the trepan has been performed upon sound persons, who were not under the influence of opium, without giving them any additional pain during the perforation of the skull. - See Fractures and Teeth.

Decomposition of Bums. After being separated from the animal, they rnay be hardened and softened, both by acids and alkalies, according to the quantity of saline matter employed, and the manner in which it is applied. Although Boerhaave assertss, that alkaline salts render them harder and tinner, and that acids make them softer and more flexible, yet these effects take place only in certain circumstances. Thus Newman found, that bones became harder and more compact by steeping them in oil of vitriol; but when this acid was in sufficient proportion, it destroyed their cohesion, and dissolved them. Dr. Lis w is, on the other hand, observed, that diluted vitriolic acid, though it rendered them remarkably soft, made them at the same time brittle; but that either in aqua fortis, or spirit of salt diluted, as well as in the acetous acid, they became flexible and soft like leather. The most effectual and cheapest method of reducing the hardest bones to a soft pap or jelly, is that effected by the action of simple water, heated in what is called Papins Digester ; a machine consisting of a strong and close iron vessel, in which the steam of boiling liquors is confined, and thus a more intense degree of heat is produced than any fluid could otherwise acquire, This effect, however, may be accomplished in a much shorter time, when, instead of pure water, alkaline solutions are employed ; yet the latter Could not properly be used in any culinary process.

If bones be exposed to a mode-rate fire, either in open vessels, or in contact with the burning fuel, they become opaque, white, and friable : by increasing the fire, they are still more reduced, and easily crumble into a powder. But, if they be at first submitted to an intense heat, such as is required to melt copper or iron, they become firm, semi-transparent, and sonorous, not unlike hard mineral stones. This curious experiment deserves the farther researches of the chemist,

A method of producing phosphorus in large quantities from bones, has been invented by M, Scheele, who employed for this purpose the vitriolic acid: it has, therefore, been doubted, whether the phosphoric acid is naturally contained in the bones, and united with calcareous earth, or whether it is generated by a combination of the vitriolic acid with a certain quantity of lime. As, however, the phosphoric acid has likewise, though in a smaller quantity, been discovered in the gastric juice of animals, there is reason to conclude (that it forms one of the elementary constituents of bones. - See BENZOINE..

Colouring of Bones. - This process may be performed either by immersing bones in the common dyeing liquors made of animal and vegetable substances, or staining them without heat, by different metallic solutions. To succeed in the former method, the bones should previously be boiled in a solutionof alum, and afterwards steeped in a decoction made of any colouring substance. Thus, for instance, to stain them of a red colour, half a pound of Brazil-wood may be boiled for an hour in a gallon of strong lime-water, in which the bone.-, are suffered to lie till they acquire a proper colour : if they assume too deep a hue of purple, it v. id be necessary to plunge them again into a solution of alum, which has the effect of bringing them to a crimson or scar et -hade.

By metallic solutions, bones may be easily spotted or variegated. - Thus a solution of silver in aquafortis, imparts, according to its strength, a brown or black colour, a solution of gold in aqua-regia, or in spirit of salt, a fine purple; a solution of copper in the acetous acid, a pleasant green; and solutions of the same metal in the vola-tile spirit of ammonia, at first a deep and beautiful blue; but which, on exposing it to the air, changes into a green, or blueish green. On touching the bone with the two 'solutions first mentioned, it acquires the desired tint in a few hours, when placed in the open air; but in those liquors made with copper, it should be steeped for at least twenty-four hours, sufficiently to imbibe the colour. In such cases as require immersion for some time, the bone may be variegated, by covering those parts which are intended to remamwhite, with wax or other matter not soluble in the staining liquor.

Econimical uses of Bones. - Be-side the various toys, and other articles of domestic economy, made of bones, they are extensively useful in many of the chemical arts; for instance, to absorb the sulphur of ferruginous ores for rendering cast-iron malleable; to form tests and cupels, or vessels for mining gold and silver with lead ; to make glasses and porcelain of a milky colour; to rectify volatile salts, and empyreumatic oils; to produce glue, etc. But the most important and beneficial uses, to which bones may be rendered subservient, are those in rural economy.

In EVELYN'S Philosophical Discourse of the Earth) we meet with a note by Dr. A. HUNTER, the editor of a new edition of this treatise, published in 1778, from which we shall extract the following accoun:: Bones are an excellent manure, though not generally known ; they should, how-. ever, not be calcined, as their virtue will be dissipated by the fire. A. St. Leger, Esq. had once laid down to grass a large i of very indifferent lime-stone land, with a crop of corn; and from this uniformly well -dressed piece he selected three rods of equal quality with the rest, and manured them with bones broken very small, at the rate of sixty bushels per acre. Upon the land thus managed, the crop was infinitely superior to the rest. The next year's grass was also more luxuriant, and has continued to preserve the same superiority for at least eight years, insomuch that in spring it is green three weeks before the rest of the field. He also dressed two acres with bones, in two different fields prepared for turnips, at sixty bushels to the acre, and found the crops incomparably more productive than the others managed in the common way. Upon grass-lands, he observed, that this kind of manure exerts its influence more powerfully in the second year than in the first. For whatever soil it be intended, the bones should be well broken, before they can be equally spread upon the land. No pieces should exceed the size or small marbles. To perform this necessary operation, he recommends the bones to be sufficiently braised, by putting them under a circular stone which, being moved round upon its edge, by means of a horse, in the manner tanners grind their bark, will very expeditiously effect the purpose. Some people break them with small hammers upon a piece of iron, but that method is inferior to grinding. Although bones of all kinds may be Used with advantage, yet those of fat cattle are doubtless the best but unground bones should never be employed, as they are of little or no service to the soil, A. St. Leger has also found it very beneficial to mix ashes wi the bones : a cart-load of the former being put to thirty or forty bushels or the latter, and heated for twenty-four hours (which may be known by the smoking of the heap), the whole should be turned. After lying ten days longer, this excellent manure will be fit for use. Lastly, Dr. Hunter remarks, that the best method of grinding bones, is that between two cast metal cylinders. And as mills are very rarely erected purposely for this operation, the apparatus may be added to any common water-mill, at a very trifling expence.