A system of practical medicine. By American authors. Vol. 1

by Unknown

When salts previously held in solution are precipitated under abnormal circumstances in the tissues of the body, the part is said to be calcified, ossified, or petrified. Although these terms are often used as equivalent, the last is to be regarded as more general than its predecessors, since it includes the deposition of other than the calcareous salts.

In the pathological ossification, as well as its physiological prototype, the carbonates and phosphates of calcium and magnesium are present in a specially formed tissue of the nature of bone-cartilage, whereas calcification occurs independently of such a new-formed tissue. The deposition of the calcareous salts takes place either in the cells or intercellular substance of living or dead tissues, when the terms calcification or ossification are applied, or as accumulations of various size in tissues or canals, which are known as concretions and calculi.

The immediate causes of the physiological deposition in the formation of bone are so obscure that only more or less probable explanatory theories are advanced, to all of which obvious objections arise. The causes of a pathological precipitation may be regarded as equally hidden. It is apparent, however, that old age usually furnishes the necessary factors. This in part may be due to the feeble nutrition associated with impairment of function in advancing years. In part it may be the result of the numerous opportunities offered in a long life for the occurrence of inflammation, the products of which are frequently infiltrated with calcareous salts. The latter are apparently kept in solution by the action of living cells, for, though presented to all in the fluids of the body, they are precipitated most constantly in dead parts or in the vicinity of those cells whose function is presumably lessened from disease or age. The solvent action of living cells is further demonstrated by the effect of the giant-cells in removing calcium salts from living or dead bone.

The causes of calcification are therefore to be regarded as local, depending upon a destruction or weakening of the cells of a part—conditions which are directly attributable to an interference with nutrition. The deposition of calcium salts thus represents a disorder of nutrition, and may be experimentally produced by agencies which occasion a necrosis of tissues.

Although the immediate causes of the precipitation of the calcium salts must be expressed somewhat vaguely, the places and effects of their accumulation are sufficiently well known, as are the resulting appearances. The presence of these salts in sufficient quantity produces a homogeneous, granular, strongly refractive appearance of the cell or intercellular substance, in addition to a greatly increased resistance to pressure. When muriatic acid is added to the affected part, the salts are dissolved, with the escape of abundant bubbles of gas when a carbonate is present, and with a rapid fading of the glistening appearance, without effervescence, when the salt is a phosphate. After the removal, the cell or intercellular substance is readily recognized, with such modifications in its appearance as may be due to the action of the strong acid. The parts in which this deposition or infiltration has taken place are either relatively normal in appearance or variously altered from disease, and the calcium salts are to be regarded as absorbed from the constituents of the food and deposited, or as taken up and transferred from the bones of the body. That both sources are drawn upon is obvious from the abnormal presence of calcareous material in the soft parts, in connection with increased density of the bones, as well as with a diminution in the density of the latter. The term calcification is more correctly applied to the presence of the salts in normal tissues other than bone, or in the products of disease not simulating bone-cartilage in structure. A pathological ossification is to be considered present when an actual new formation of bone has taken place so limited and so situated as not to suggest a tumor of bone, or when the calcium salts are deposited in a new-formed tissue whose structure stimulates that of bone-cartilage.

Tissues which may become calcified are, in the first instance, the connective tissues, and of these fibrous tissue and cartilage are especially liable. Epithelial, muscle—in particular the unstriped variety—and ganglion-cells may also become calcified. The frequency with which blood-vessels, especially arteries, are affected is such that it is regarded as almost normal in advancing years that calcareous material should be deposited within the vascular walls. A distinction is drawn between an ossification and a calcification of the blood-vessels. The former term should be limited to the osteoid plates so often found as circumscribed thickenings of the aortic intima, and which are obviously new-formed patches of fibrous tissue in which the calcium salts are accumulated. A calcified artery, on the contrary, is one usually of a size varying between that of the common iliac and the temporal arteries, whose wall has become rigid and unyielding, suggestive of a pipe-stem, from the presence of calcareous deposits in the muscular middle coat.

From the frequency with which the osseous plates of the aorta are associated with the fatty and fibrous changes in chronic inflammation of the intima, the so-called atheromatous degeneration of the same, it is customary to speak of the calcified artery at the wrist or temple as an atheromatous artery or as evincing an atheromatous degeneration. The common feature in the aortic changes and in the calcified muscular coat is the element of age. They are frequently, though not necessarily, associated. The one is the result of an inflammatory process productive of a new, fibrous, tissue in which the calcium salts are infiltrated; while the other is due to a deposition of the latter in the normal, pre-existing, muscular elements of the vessel.

Calcification and ossification of blood-vessels are frequent when the latter become dilated, as in aneurisms, whether these occur as circumscribed tumors or as a serpentine elongation and widening of the affected vessel.

Cartilage is also a tissue which presents a double relation to calcareous deposition. On the one hand, there may exist an ossification resulting from the extension of a growth of bone from the perichondrium into the cartilage. The structure of this bone presents all the details found in normal bone—lacunæ, lamellæ, and marrow-spaces. On the other hand, a section of the cartilage, especially the costal cartilages, may contain opaque, gray, or grayish-yellow patches, grating under the knife, which are wholly due to the presence of calcium salts in the hyaline intercellular substance of the cartilage. This calcification of the cartilage, which may also involve the capsules of the cells, is frequently associated with an ossification, although this relation is in no way essential.

Calcification of the placenta, of the fibrous framework of the lungs, of the mucous membrane of the stomach, or of the atrophied glomeruli of the kidney, are well-recognized instances of the infiltration of calcareous material in normal or atrophied tissues. On the contrary, ossification of the fibrous inflammatory products of the pleura, pericardium, and peritoneum are instances of a pathological bone-formation, analogous in its nature to that met with in the intima of the aorta. The fibrinous and fibrino-cellular products of the inflammation of serous surfaces are favorable positions for the deposition of calcium salts, as are thrombi arising from the walls of blood-vessels. The latter are rather instances of the calcification of dead parts, analogous to the members of the group which includes the formation of calculi and concretions, the calcification of the dead foetus in abdominal parturition, of cheesy lymphatic glands, and of cheesy material in the lungs and elsewhere. Finally, there remains the calcification of tumors of the most varied nature, the salts being present either in living or dead parts of the tumor.