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GROWTH OF CARTILAGE.

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mode of growth, not only in vegetables, but also in the physiological and pathological formations of the animal body.

FIG. 9.

In the following preparation-a piece of costal cartilage, in a state of morbid growth-changes are evident even to the naked eye, namely, little protuberances upon the surface of the cartilage. Corresponding to these the microscope shows a proliferation of cartilage-cells, and we find the same forms as in the vegetable cells; large groups of cellular elements, each of which has proceeded from a single previously existing cell, arranged in several rows, and differing from proliferating vegetable cells only in this-that there

is intercellular substance between the individual groups. In the cells we can as before distinguish the external capsule, which, indeed, in the case of many cells, is composed of two, three, or more layers, and within them only does the real cell come with its membrane, contents, nucleus, and nucleolus.

In the following object you see the young ova of a frog, before the secretion of the yolk-granules has begun. The very large ovum (Eizelle) (Fig. 10, C) contains a nucleus likewise very large, in which a number of little vesicles are dispersed and tolerably thick, opaque contents, beginning, at a certain spot, to become granular and brown. Around

Fig. 9. Proliferation of cartilage; from the costal cartilage of an adult. Large groups of cartilage-cells within a common envelope (wrongly so-called parent-cells), produced from single cells by successive subdivisions. At the edge, one of these groups has been cut through, and in it is seen a cartilagecell invested by a number of capsular layers (external secreted masses). 300 diameters.

the cell may be remarked the relatively thin, connective tissue of the Graafian vesicle, with a hardly visible layer of

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epithelium. In the neighbourhood are lying several smaller ova, which show the gradual progress of their growth.

FIG. 11.

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As a contrast to these gigantic cells, I place before you an object from the bed-side; cells. from fresh catarrhal sputa. You see cells in comparison very small, which, with a higher

Fig. 10. Young ova from the ovary of a frog. 4. A very young ovum. B. A larger one. C. A still larger one, with commencing secretion of brown granules at one pole (e), and shrunken condition of the vitelline membrane from the imbibition of water. a. Membrane of the follicle. b. Vitelline 'membrane. c. Membrane of the nucleus. d. Nucleolus. S. Ovary. 150 diameters.

Fig. 11. Cells from fresh catarrhal sputa. 4. Pus-corpuscles. a. Quite fresh. b. When treated with acetic acid. Within the membrane the contents have cleared up, and three little nuclei are seen. B. Mucus-corpuscles. a. A simple one. b. Containing pigment granules. 300 diameters.

LARGE AND SMALL ANIMAL CELLS.

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power, prove to be of a perfectly globular shape, and, in which, after the addition of water and reagents, a membrane, nuclei, and, when fresh, cloudy contents can clearly be distinguished. Most of the small cells belong, according to the prevailing terminology, to the category of pus-corpuscles; the larger ones, which we may designate mucus-corpuscles or catarrhal cells, are partly filled with fat or greyish-black pigment, in the form of granules.

These structures, however small their size, possess all the typical peculiarities of the large ones; all the characters of a cell displayed by the large ones again present themselves in them. But this is, in my opinion, the most essential point-that, whether we compare large or small, pathological or physiological, cells, we always find this correspondence between them.

LECTURE II.

FEBRUARY 17, 1858.

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Falsity of the view that tissues and fibres are made up of globules (elementary granules). The investment theory (Umhüllungstheorie).- Equivocal [spontaneous] generation of cells.-The law of continuous development. General classification of the tissues.-The three categories of General Histology. -Special tissues.-Organs and systems, or apparatuses.

The EPITHELIAL TISSUES.-Squamous, cylindrical, and transitionary epithelium. Epidermis and rete Malpighii. - Nails, and their diseases.— Crystalline lens.-Pigment.-Gland-cells.

The CONNECTIVE TISSUES.-The theories of Schwann, Henle, and Reichert. -My theory.-Connective tissue as intercellular substance.-Cartilage (hyaline, fibro- and reticular).-Mucous tissue.-Adipose tissue.-Anastomosis of cells; juice-conveying system of tubes or canals.

IN

In my first lecture, gentlemen, I laid before you the general points to be noted with regard to the nature and origin of cells and their constituents. Allow me now to preface our further considerations with a review of the animal tissues in general, and this both in their physiological and pathological relations.

The most important obstacles which, until quite recently, existed in this quarter, were by no means chiefly of a pathological nature. I am convinced that pathological conditions would have been mastered with far less difficulty if it had not, until quite lately, been utterly impossible to give a simple and comprehensive sketch of the physiological

ELEMENTARY FIBRES AND GLOBULES.

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tissues. The old views, which have in part come down to us from the last century, have exercised such a preponderating influence upon that part of histology which is, in a pathological point of view, the most important, that not even yet has unanimity been arrived at, and you will therefore be constrained, after you have inspected the preparations I shall lay before you, to come to your own conclusions as to how far that which I have to communicate to you is founded upon real observation.

If you read the Elementa Physiologia' of Haller, you will find, where the elements of the body are treated of,, the most prominent position in the whole work assigned to fibres, the very characteristic expression being there made use of, that the fibre (fibra) is to the physiologist what the line is to the geometrician.

This conception was soon still further expanded, and the doctrine that fibres serve as the groundwork of nearly all the parts of the body, and that the most various tissues are reducible to fibres as their ultimate constituents, was longest maintained in the case of the very tissue in which, as it has turned out, the pathological difficulties were the greatest in the so-called cellular tissue.

In the course of the last ten years of the last century there-arose, however, a certain degree of reaction against this fibre-theory, and in the school of natural philosophers another element soon attained to honour, though it had its origin in far more speculative views than the former, namely, the globule. Whilst some still clung to their fibres, others, as in more recent times Milne Edwards, thought fit to go so far as to suppose the fibres, in their turn, to be made up of globules ranged in lines. This view was in part attributable to optical illusions in microscopical observation. The objectionable method which prevailed during the whole of the last and a part of the present century—of making observations (with but indifferent instruments) in the

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