Importance and interest of Osteology. WHOEVER Would become a good surgeon, must make himself master of human osteology. It is not only his first, but his principal and constant professional study. During his dissections he is continually referring to the skeleton. He cannot reduce the simplest dislocation without a competent knowledge of the bones. The subject appears dry and tedious to a beginner-what study, indeed, does not? — but a little progress will convince him that, so far from being dry, it is full of interest, not only as conducive to professional success, but for its own sake. No part of creation displays more manifest design than the human skeleton. Undertaken in a right spirit, the study of it becomes, with many, a favourite pursuit, — leads us to look a little beyond "final purposes," and creates a natural longing to know something of the skeleton of the lower animals, that we may the better judge of the admirable construction of our own; for it is only by comparison that we can judge. When the great truth unfolds itself, that our own structure is but a modification of the " one common pattern" upon which all vertebrate animals are formed, we cannot but feel with the philosophic poet, that ""Tis the sublime of man, Our noontide majesty, to know ourselves Parts and proportions of a wondrous whole." B COLERIDGE. Use of the bones. The bones form a framework for the moulding and adequate support of the soft parts of the body; they form cavities for the lodgment and protection of delicate organs,-e. g., the skull for the protection of the brain; the vertebral canal for the protection of the spinal cord; the orbit for the protection of the eye; the chambers in the temporal bone for the protection of the internal ear; the chest for the protection of the heart and lungs, &c.: they form the joints for the locomotion of the whole body, as well as for the movement of its individual parts: they form levers for the action of the muscles. General composition of bone. Its analysis. Bone is composed of a basis of animal matter impregnated with "bone earth" or phosphate of lime. The first ingredient makes it tenacious and elastic; the second gives it the requisite hardness. The analysis is easily made. Place a bone in a solution of one part of dilute hydrochloric acid to five or six of distilled water; in a few days all the earthy part will be dissolved out by the acid, and the animal part will be left. The bone will be scarcely altered in shape or colour, but it can be bent and twisted in any direction. On the other hand, to get rid of the animal matter we have merely to boil the bone for a long time; or the bone may be calcined till all the animal matter is burnt out. In either of these ways the animal constituent of the bone will be removed, and nothing left but the earthy. The animal matter consists of gelatin (or glutin), which is nearly all soluble in boiling water. Everyone knows that soup may be made out of bones. Notwithstanding their antiquity, fossil bones are found to contain nearly as much animal matter as recent bones. Gimbernat made soup from the gelatin of the mastodon's tooth, as Dr. Buckland afterwards did from the fossil bones of the hyæna. Relative proporAs to the relative proportions of the animal and earthy matter in bone, the best chemists agree that the animal part forms about one third, the earthy two thirds. Are these proportions constant? Do they vary at different periods of life, and in different bones of the skeleton? It is the generally received opinion that they do vary. It is believed that the animal element predominates in the bones at the beginning of life, and the earthy element at the decline. This is assigned as the reason why the bones tions of the animal and earthy mat ter. of children are so elastic, so liable to indent, as in the case of the skullcap, and to bend like a green stick rather than break like the bones of the aged. Some recent investigators*, however, have impugned the correctness of this opinion. Their analyses go to prove that equal weights of bone tissue contain, at all ages, and in all bones, nearly the same relative proportions of animal and earthy matter. A particle of bone, they say, is a definite, not a variable compound. The hardness and compactness of bone depend, not upon the variations of its earthy ingredient, but upon the quantity of bone condensed in a given space. The peculiarity of the bones of children arises from the greater sponginess of their texture, and from the layers of cartilage introduced in appropriate parts to facilitate growth and to break shocks. The following is Lehman's† analysis of adult human bone: Dr. Bostock's analysis of ricketty bones. In the disease of early life called "rickets," in which the bones bend and become distorted, from deficiency of earthy matter, Dr. Bostock found the proportions of animal and earthy matter to be — Animal matter 79.75 per cent. * Dr. Stark, "Edinb. Med. and Surg. Journal," April, 1845; Nélaton, "Elements de Pathologie," t. i. p. 636. Mr. R. Tuson, Demonstrator of Chemistry at St. Bartholomew's Hospital, has given me the subjoined analysis of 100 parts, by weight, of human long bones of different ages : Of all animals, the bones of birds (especially of the predaceous kind) contain the largest proportion of earthy matter. Hence their great compactness and white colour. The bones of mammalia contain the next proportion: those of reptiles the next; and least of all those of fishes. Importance of Of the earthy ingredients of bone, the phosphosphate of lime. phate of lime holds by far the first rank; hence it is commonly called "bone earth." Adult bone contains 57 per cent. of it, and not more than 8 per cent. of the carbonate of lime. The latter is the principal ingredient in the hardening of shells. But the phosphate of lime is made use of to harden bone, because it forms a harder compound with animal matter than the carbonate. What can be harder than the enamel of the teeth? And this consists of a very large proportion of phosphate of lime combined with animal matter. According to Berzelius, there is only 2 per cent. of animal matter in the enamel, and of the remaining 98 parts, 881 consist of phosphate of lime. Phosphate of lime enters not only as the principal earthy ingredient into the composition of bone, but is contained, more or less, in nearly all the tissues of the body. Of all inorganic materials it appears to be the most essential both for vegetable and animal life. Therefore it is not only a most important article of diet, but also a necessary manure. "Those parts of plants which experience has taught us to be the most nutritious, contain the largest proportion of the phosphates, such as bread-corn, peas, beans, and lentils." It has been ascertained by experiment, that if animals have their entire supply of phosphate of lime cut off, after some weeks of illness, they are attacked with diarrhoea, which soon kills them. Their bones are found very much softened; and it is not unlikely that the phosphate is absorbed from their bones to supply other more important structures, such as the nerves and muscles. It is the quantity of phosphate of lime in the bones which makes them so valuable as manure. The bones are boiled to extract the gelatin or glue; afterwards they are crushed in a mill, and, as "bone dust," form an extensive article of commerce. * Liebig's Letters on Chemistry, p. 522. |