英文科學(xué)讀本 第六冊(cè)·Lesson 40 Bones

Lesson 40 Bones

The bones of almost all animals are serviceable in some way to man. Indeed, the position which bone holds among the economic products of animals is by no means an unimportant one. Bone enters largely into many varieties of manufacture, and so great is the demand for it, that in addition to the home supply from slaughtered animals, England imports immense cargoes every year from many parts of the world. England's total annual imports of bones from all sources amount to upwards of 100,000 tons, and are valued at about ￡700,000 sterling. The bones of commerce are chiefly those of the horse, ox, buffalo, elephant, giraffe, and hippopotamus.

We use bone in its natural state for knife-handles, spoons, brushes for teeth and nails, combs, fans, buttons, paper-knives, etc. The bones usually employed for these purposes are the shank and buttock bones of oxen. It is estimated that in Sheffield alone no less than two million shank-bones are worked up in this way every year. The manufacture of bone buttons is a very important and extensive industry, and gives employment to immense numbers of work-people. Birmingham and Sheffield turn out bone buttons in ton-loads every year.

The fresh or green bones, as they come to the hands of the manufacturer, contain a large amount of fat and before they can be of any use to him this must all be removed. The fat is extracted by boiling the bones. They are usually boiled for about twenty-four hours, and the fat which rises to the surface is skimmed off when cool. The hollow shank-bones of the ox are carefully boiled by themselves, and the skimmings from them yield a valuable fat, which forms the material for the manufacture of butterine, and usually fetches about forty shillings per hundredweight. The fat from other bones, which is coarser and of inferior quality, is sold to the soap-makers, and is worth about thirty shillings per hundredweight.

Bones are also largely used in the manufacture of artificial manures. Our investigations into the nature and composition of bone have shown us that in addition to animal or organic matter—ossein—it contains two-thirds of its weight of mineral matter. It is this mineral matter that makes the bone dense, hard, and rigid—the very material for the framework of the body of the animal, providing support, protection, and means of locomotion.

We have seen, too, how a bone behaves when it is placed in a clear, red fire. The whole of the organic matter in it burns away, leaving a white brittle substance, which the fire will not consume. This is the earthy or mineral matter of the bone. It is known as bone-ash, or bone-earth, and consists chiefly of phosphate of lime. Bone-ash is obtained in this way by burning bones, and is prized by the farmer as a very useful manure for his land.

You remember, no doubt, that by steeping a bone in dilute muriatic acid, we are able to dissolve all this mineral matter out of it, leaving only the tough, flexible, gristly ossein behind. When the steeping is over, all the mineral matter of the bone is in a state of solution in the liquid itself. This will help you to understand the preparation of another very valuable manure, known as super-phosphate of lime. The bones for this purpose, instead of being burned, are merely crushed into small pieces and put into dilute sulphuric acid. The acid, of course, dissolves all the mineral matter out of the bone, the ultimate product being the valuable super-phosphate of lime.

Animal charcoal, a substance largely used in the arts, is made by burning bones in closed, air-tight retorts for twelve hours, the gases being allowed to pass off as they are formed by the burning, so that nothing is left behind but the carbon of the bone. This is afterwards crushed into small grains, and is known as animal charcoal.

Animal charcoal is employed in the sugar refineries. The syrup of the raw sugar is filtered through this charcoal, which extracts all its brown color and leaves it white. The powdery dust formed by crushing the charcoal is known as bone-black, and is used in the manufacture of blacking.

Now let us think once more of those great factories where bones are made into knife-handles, spoons, buttons, and other articles of use. Of course the bones must be sawn, cut, carved, and shaved in; various ways in the preparation of such articles; and the workman makes cuttings, chips, scraps, shavings, and sawdust, just as he would with other materials.

None of this, however, is wasted. All is collected up for further use.

These scraps of bone are soaked in dilute muriatic acid, which dissolves out all the mineral matter and leaves behind only the animal matter of the bone—the tough, flexible ossein. This is first washed and cleansed in lime-water, and afterwards carefully boiled. Ossein when boiled yields a new substance—gelatine or jelly. This jelly becomes a valuable article of food, very rich in tissue-forming properties. It is first flavored with orange, lemon, vanilla, or some such flavoring, and then poured while warm into bottles, and left to cool. These are the jellies we see in bottles in the grocers' shops.