of an inch. The inter-cellular substance was hyaline, and in a few places indistinctly fibrous. The cells were irregularly arranged in it, and thus contrasted remarkably with the vertical groups in the deep cells of healthy parts. Many of the large round cells, on the cut surfaces, projected considerably, and they no doubt discharged their corpuscles into the fibro-nucleated mass connecting the surfaces; for, on examination, the mass was found to be very transparent, occasionally containing imperfect fibres, and always studded with irregular corpuscles, differing from those within the cells, in being smaller and more irregular. The changes observed in the superficial layers of the cartilage were,-slight enlargement of the cells, especially in width, with the production of granules in their interior, the inter-cellular substance becoming indistinctly fibrous or granular, so as partly to conceal the cells.-(Fig. L.)

Fig. L.-Appearance of the cartilage of the patella of the dog on the edges of an incision, made forty-nine days before death.

In an instance in which the patella was dislocated outwards, and had the middle of its posterior surface firmly pressed upon the edge of the articular surface of the condyle of the femur during flexion, a small flap, made by incision, was found directed upwards, and lay in such a position as to make pressure upon another flap, situated higher up, causing its entire removal. The structure of the flap which was turned up was changed in a similar way to that of those before described. The whole upper part of the cartilage was loosened at its attachment to the bone. Its cells were indistinct in some parts, having become very granular, or reduced to mere patches of granules, which lay in a fibrous or hyaline matrix, the hyaline substance having become converted into fibres, whilst the cells were reduced to small patches of granules.

In another instance, the patella was dislocated internally, and the external half of its articular surface, which moved on the condyle during flexion and extension, presented a perfectly smooth and po

NEW SERIES.-NO. III. MARCH 1850.

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lished surface on a level with the other parts of the cartilage. This surface rung like bone on being struck with a knife; but, on being examined, still presented the usual arrangement of superficial and deep cells of cartilage, in a few places; whilst, in others, the cells of the whole thickness of the cartilage were distinctly calcified, explaining why this part of the surface was not depressed, as it would have been if the cartilage had been removed so as to have exposed the bone. The deep cells still retained their columnar arrangement even when completely calcified. On the surface of the uncalcified parts of the cartilage, large rounded cells existed, measuring in some places, 4th of an inch, and crowded with finely granular corpuscles. A similar calcification of the cells of the cartilage of the patella of the rabbit was noticed, after incision and inflammation of the joint resulting from this and the application of actual cautery to the cartilage of the femur. As the cartilage became calcified, the texture assumed the appearance of some forms of fibro-cartilage, with very indistinct fibres.

The changes produced by the application of actual cautery to a limited space on the cartilage of the femur or patella, so as to destroy it through nearly its whole thickness, were ascertained in dogs and rabbits in ten instances. It was found that inflammation by no means necessarily took place when the cauterised spot did not exceed one-eighth of an inch in its greatest diameter, and when dislocation did not result; but that when the application was made to a more extensive surface, even superficially, a considerable quantity of lymph was thrown out by inflammation, and was mixed with the elements of the diseased cartilages. The cases in which neither inflammation nor displacement occurred, were those in which the changes in the texture of the cartilage were best observed, though these were essentially similar, in all the cases, in animals of the same species.

No change of texture could be distinctly seen on the most careful examination made on the 2nd and 7th days after the application of the cautery; but a marked change was found at periods between the 37th and 98th days, and was always of the same character. Thus, on the 39th and 49th days, the cartilage presented a reddened and depressed spot at the point of application of the cautery; and, for the distance of a line around that part, it was slightly diminished in its thickness. Beyond this, every part of the texture appeared perfectly healthy, and consisted of a series of superficial cells, parallel to the surface, measuring 100th of an inch by 7th, and rarely containing a distinct nucleus or granule ;-also of deep cells, arranged in vertical groups, as usual, these groups measuring 16th by 30th of an inch, and lying in hyaline substance, like the cells of the surface. On proceeding in the examination, from the healthy towards the cauterised part, the deep cells were further separated, and constituted rounded groups rather than vertical columns; nearer still, The cells in the rounded groups became separated, enlarged, and re

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Fig. LI.

gularly disseminated through the hyaline matrix; whilst, where the cartilage was diminished in thickness, the superficial cells were no longer seen, and the deeper ones were very much enlarged, rounded, or oblong, and crowded with corpuscles. The largest measured th by both of an inch, and the average size of their contained corpuscles was 3500th of an inch. The cells of largest size were found at an abrupt line, which constituted the margin of the surface to which the cautery had been applied; those seen on passing away from this point gradually diminishing in size-(Fig. LI). Beyond the largest cells, in the other direction, was a mass of corpuscles lying in a hyaline matrix, which, at a little distance, presented traces of fibres; whilst perfect fibres, densely interwoven, constituted a fibrous membrane at the bottom of the cauterised spot. In the fibrous membrane, no further traces of corpuscles could be seen than small patches of granules; and, in many preparations, these were not visible without the action of acetic acid. Between the part consisting of perfect fibres, and that composed of corpuscles dis

Fig. LI.-Shows the cartilage of the femoral trochlear on the edge of a spot to which actual cautery was applied forty-nine days before death.

charged into a hyaline matrix, the corpuscles were found gradually becoming smaller and elongated, like nuclei of fibres; or granular, shrivelled, and at last reduced to mere clusters of granules. The texture of the bone under the cartilage thus changed, was dense and apparently healthy.

In cases where inflammation had taken place, the cauterised and the neighbouring parts were covered with a dense fibrous mass, which could be stripped from the bone with forceps. The structure of the superficial and deep portions of this mass was very different, the superficial part consisting of fibrous tissue, with nuclei, elongated in the direction of the fibres, and brought into view by the addition of acetic acid; and the deeper ones having nuclei interspersed amongst fibres, and lying at right angles, or obliquely, in relation to each other, capable also of being traced in all stages of their formation, from the discharged corpuscles of cartilage cells.1

In a knee-joint, in which internal dislocation of the patella became permanent, a dimple-like depression on the external part of the car

It is difficult to convey an accurate idea of the difference in appearance of the fibres and nuclei of the fibrous tissue, which was the product of inflammation, and of that which resulted from changes in the texture of the cartilage, notwithstanding that a few examinations of both, with the attention directed to the nuclei, readily serves to distinguish them.

tilage of the inner glenoid cavity of the tibia, indicated the point on which the condyle of the femur had rested. The superficial cells of this part were spherical, 1200th of an inch in diameter, and contained three or four finely granular corpuscles, whilst the superficial cells of all the surrounding parts presented the usual horizontal arrangement. (Fig. LII.)

Fig LII.

In another case, the patella remained dislocated internally, and the cartilage of both glenoid cavities was considerably changed, without any other apparent cause than the unequal pressure made upon the surfaces. The cartilage of the external cavity was softened; its superficial parts were granular, and their cells largely developed and loosened, as shown in Figs. XI. and XII. These cells measured 1000th by 1700th of an inch, and contained imperfect corpuscles. The deeper parts appeared mottled, but their cells were unchanged. The cartilage of the internal glenoid cavity was absent over about half the surface in front and internally, as well as under the semi-lunar cartilages. glenoid cavity of the tibia, at a dimple. Where it existed, the superficial cells were removed, and bands and fibres, formed of hyaline substance, projected from the surface for th of an inch. The cells in the deepest parts lay in vertical columns, in hyaline substance, which was mottled and indistinct, and those placed more superficially, were enlarged, and measured from 14th to 7th of an inch. They contained corpuscles, and were irregularly distributed in the texture.

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After actual cautery had been applied, for upwards of forty days, to the central part of the cartilages of the knee-joints of rabbits, similar changes to those detailed above were found; but in many parts the surface retained its level, and became calcareous, owing to deposition of calcareous matter in the walls of the cells and in their nuclei, converting them into bodies precisely like osseous lacunæ. This calcification could be observed in all stages; taking place, in some parts, where the arrangement of the cells had become irregular, and in others, where they still formed columns arranged vertically. It will be recollected that a similar formation of lacunæ from cartilage cells was before shown to take place in the costal cartilages, and in the fibro-cartilage of the ear.

In two cases, in which central portions of the articular cartilages of the knee-joint had been cut away down to the bone, 140 days before death, precisely the same changes as are detailed above, took

in the adjacent parts, the only difference being, that many of

the corpuscles which had been set free had become enlarged, and occupied spaces between the fibres, so as to give the texture the characters of fibro-cartilage.

Intense inflammation, with effusion of lymph, was the result of the temporary application of hydrochloric acid, liquor potassæ, or liquor ammonia, to the cartilages of the knee-joints of rabbits. The cartilage, in different places, underwent all the before-mentioned changes, being completely calcified in many parts; whilst, in others, there were various stages of production of granules in the cells, or reduction of the cells or nuclei to patches of granules found amongst fibres. In some places, the cells were large, and crowded with corpuscles;-in others, the corpuscles were interspersed amongst fibres, and were undergoing the usual conversion into nuclei ;-and many parts consisted of cells lying in a very dark inter-cellular substance, which obstructed the passage of the light, even in very thin sections. Such parts were instantly rendered transparent by the action of acetic acid; the acetic solution thus obtained, giving, after neutralisation by ammonia, and the addition of oxalate of ammonia, numbers of beautifully octohedral crystals insoluble in acetic acid, and evidently those of oxalate of lime. It thus appears that the darkening of the hyaline substance is owing to the deposition of calcareous salts. In the cases just noticed, the application of the fluid was intended to be confined to the cartilages of the patella and femur, but a small quantity ran into the joints, apparently in consequence of which the superficial cells of the posterior part of the femoral condyles, and those of the cartilages of the tibia, were very much enlarged, widely separated, and connected only by a gelatinous and hyaline substance, from which the cells escaped readily by pressure. To the naked eye, these parts presented no trace of disease.

With a view to ascertain the mode of extension of disease from the bone to articular cartilage, I passed a thick brass wire, in two instances, in the dog, under the trochlear surface of the femur, at the distance of half-a-line from the cartilage; but, on examination of the parts, at periods of nineteen and thirty-four days afterwards, no change could be seen in the cartilage, except that its superficial cells in the neighbourhood of the part, were enlarged and granular. It is very probable, however, that this was the result of inflammation in the synovial membrane, as the deeper parts of the cartilage were certainly unchanged in structure, in both instances. After thirty-four days, the bone in contact with the wire was softened; and, in both cases, the whole lower end of the femur was highly vascular. Considerable lameness followed both these operations, and continued for a week or ten days, after which it could scarcely be perceived, unless during unusual movements of the limbs.

From what has preceded, it is obvious that anormal nutritive changes can be induced in the cartilages of the lower animals, with considerable facility, by irritations of various kinds-such as the making of incisions into them, the insertion of setons, the application