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Fig. 130.

layer (of the periosteum) increases in thickness and swells up, and then it is said an exudation has taken place, it being taken for granted, that every swelling proves the occurrence of an exudation, and that the exudation here lies between the periosteum and the bone. But if you set to work and analyze the substance deposited, no trace of any plastic exudation is found; the swollen spot appears on the contrary organized in its whole thickness from without inwards, and this most distinctly close to the bone, whilst towards the surface of the periosteum the structural relations can be less readily unravelled. This swelling may

under certain circumstances increase to a very considerable extent. In periostitis we do not unfrequently see,you know, regular nodes formed, and one need only recall the more physiological history of callus after fracture. In either of these cases we seek in vain for an exudation. If the thickened layers are traced in the direction of that part of the periosteum which still remains unthickened, we can very distinctly see what Duhamel long ago exhibited in a very beautiful manner, but is forgotten over and over again, namely, that the layers which constitute the thickening are ultimately all

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Fig. 130. Vertical section through the periosteum and periosteal surface of a parietal bone from a child. A. The proliferating layer of the periosteum with anastomosing networks of cells and division of nuclei. B. Formation of the osteoid layer by means of the sclerosis of the intercellular substance. 300 diameters.

1 Sclerosis signifies thickening with condensation.— From a MS. note by the Author.

OSTEOID TISSUE. 425

of them continued into the layers of the periosteum. As little as the periosteum is unorganized, so little are the thickened layers without organization. Microscopical examination shews at the surface of the bone a slightly striated basis-substance, and in it, numerous, small, cellular elements; the farther we recede from the bone, the more do divisions of cells occur, and at last we meet with the simple, very small connective-tissue-corpuscles of the periosteum. The division follows the same course as in cartilage, only that the dividing cells of the periosteum are very delicate. The greater the irritation, the greater also the proliferation, and the more considerable the swelling of the growing spot.

The cells which thus result from the proliferation of the periosteal corpuscles are converted into bone-corpuscles exactly in the way I described when speaking of the marrow. In the neighbourhood of the surface of the bone the intercellular substance grows dense and becomes almost cartilaginous, the cells throw out processes, become stellate, and at last the calcification of the intercellular substance ensues. If the irritation is very great, the corpuscles grow very considerably, and then real cartilage is produced; the corpuscles enlarge to such an extent that they grow into large, oval or round cells, and each of these forms a capsule around itself by secretion. In this manner cartilage may arise in the periosteum also, by means of a direct transformation of its proliferating layers, but it is by no means necessary that real, true cartilage should be produced; generally only the osteoid transformation takes place, when the intercellular substance becomes sclerotic and at once calcifies.

Thus it is, that on the surface of every growing bone, as Flourens particularly has shewn, new bone is continually deposited layer after layer, and that the new layers grow round the old bone in such a way, that a ring, which is early put around the bone, after a time lies inside it, enclosed by the young layers which have formed outside around it. These are connected with the old bone by means of little columns which give the whole a pumicestone like appearance, and here too the subsequent condensation into cortical substance is accomplished by means of the formation—within the individual cavities bounded by the little columns—of concentric layers of osseous substance out of the periosteal marrow.

These are the normal and pathological processes which we recognize in the formation of bone. From them you may gather, that we have in them to do with a series of permutations or substitutions, which lead in one case to a higher, in another, to a lower form of structure, but are however constantly connected with one another, and, according to the conditions which operate upon the parts, assume sometimes one aspect, sometimes another. It is in our power to incite individual portions of cartilage to ossify, or to transform themselves into a soft tissue. In this whole series the marrow stands alone as the type of the heterologous forms, inasmuch as it contains the smallest and least characteristic cells. The young medullary tissue presents the same structure as the young formations, with which all heterologous tissues begin, and since, as I have already hinted, it at the same time constitutes the real type of all granulations, it may be said that, wherever newformations are about to arise on a large scale, a substitution analogous to the type of young medullary tissue (granulation) also takes place; and that, no matter how great the solidity possessed by the old tissue, a kind of proliferation nevertheless always takes place, which produces the germs of the subsequent elements.

LECTURE XIX.

APRIL 24, 1858.

PATHOLOGICAL, AND ESPECIALLY HETEROLOGOUS,
NEW-FORMATION.

Consideration of some forms of pathological formation of bone. Soft osteoma
of the maxillae.—Rickets.—Formation of callus after fracture.

Theory of substitutive new-formation in opposition to exudative.—Destructive nature of new-formations. — Homology and heterology (malignity).— Ulceration.—Mollities ossium.—Proliferation and luxuriation.—Medulla of bones, and pus.

Suppuration.—Its two forms: superficial, occurring in epithelium; and deep, in connective tissue.—Eroding suppuration (skin, mucous membrane): pusand mucus-corpuscles in their relations to epithelium.—Ulcerative suppuration.—Solvent properties of pus.

Connection of destruction with pathological growth and proliferation.—Correspondence of the first stage in pus, cancer, sarcoma, &c, —Possible duration of the life of pathologically new-formed elements, and of pathological new-formations considered as wholes (tumours).—Compound nature of the larger tuberous1 tumours (Geschwulstknoten), and miliary character of the real foci (Heerde).—Conditions of growth and recurrence: contagiousness of new-formations and importance of the anastomoses of cells.— Cellular pathology in opposition to the humoral and heuristic. —General infection of the body.—Parasitism and autonomy of new-formations.

Gentlemen,—I will to-day begin by laying some pathological preparations before you, for which I remained in your debt last time.

I begin with an interesting object which has lately come into my hands, and exhibits with a distinctness which I

1 Tuberous, in contradistinction to infiltrated, tumours (infiltrations;.—From a MS. note by the Author.

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have rarely had occasion to witness, the transitions from periosteal connective tissue into osteoid tissue, and this too with a peculiar modification, inasmuch as calcification has not taken place in large portions of the parts which already possess the structure of bone. The preparation comes from a tumour in the jaw of a goat, and contributes towards our knowledge of the transitions from connective tissue into osteoid tissue about the same information, that the history of rickets has supplied us with concerning the transformation of cartilage. The tumour which affected the superior and inferior maxillae, but each separately, has such little density, that it can be cut with great facility, and only in a few places does the knife meet with greater resistance. On making thin sections, we see even with the naked eye that more and less dense portions alternate with each other, so that the whole has a reticular appearance. When examined under the microscope with a

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Fig. 131. Section from a soft osteoma from the jaw of a goat—shewing the characters of periosteal ossification. Networks of osteoid trabecular with jagged cells enclose primary medullary spaces, filled with fibrous connective tissue. The dark parts represent calcified and completely developed osseous tissue. 150 diameters.

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