reason to entertain any doubt as to his being so for more than twenty years, when, in the month of February 1851, Dr Handyside asked me to see him, on account of an alarming change that had taken place in the condition of the tumour. The thigh was considerably swelled and painful, especially when pressure was applied on the seat of the exostosis, which could not be felt distinctly in consequence of the thickening around it that had taken place, together with the effusion of some fluid that was detected by a deep fluctuation. In explanation of this circumstance, as it was stated that the patient had latterly been leading a life of much greater exertion, particularly in walking, than he was previously wont to do, Dr Handyside enjoined rest, and, after a time, applied a blister. We thought that there was something seriously wrong, and were not free from the apprehension of cerebriform degeneration, but resolved to try the farther effect of rest, with gentle pressure. In the course of a few weeks the swelling and tenderness disappeared, the fluctuation could no longer be perceived, and the exostosis was felt no less distinctly defined than in former times. I felt quite at a loss to account for this case, until the following one completely explained it. In November of last year Dr Duncan asked me to take under my charge, in the hospital, a female servant who, in crossing the ferry from Fife, had received a blow, which was supposed to have detached an exostosis from its usual seat of attachment, above the knee, on the inner side of the thigh bone. As the limb was very much swelled, and extremely painful, I feared that delay might lead to suppuration, and therefore cut freely down to the exostosis; but in doing so was surprised to find a quantity of serous fluid, tinged with blood, lying between it and the surface immediately surrounding it. The whole truth at once appeared, and I no longer felt any difficulty in accounting for the smooth shining surface presented by growths of the kind in question, or for the fluctuation which, in the former case, had so much perplexed Dr Handyside and myself. It was plain that a synovial membrane surrounded the exostosis, and was reflected from its neck, so as to afford a double covering, just as on the joints-the half of one being thus represented by the osseous growth, its crust of cartilage, and investing membrane. I hope that the condition of what may be called the pedunculated exostosis, thus fully ascertained, may be of service, not only in its diagnosis, but also with reference to the means of remedy, since the complete insulation from surrounding textures, except at the comparatively small point of its attachment to the bone affords great encouragement to attempt removal, even under circumstances apparently much opposed to success. Thus, in the case of a young lady from Lancashire I saw lately with Dr Simpson, there was an exostosis at the neck of the humerus, which pressed upon the axillary nerves, so as to occasion great and increasing distress; and, from this position, had been deemed beyond the reach of removal. 1854.] STRUCTURAL EXAMINATION OF AN EXOSTOSIS. But, having ascertained that the point of attachment was at the posterior surface of the bone, I made an incision between the deltoid and triceps, exposed the neck, detached it by cutting pliers, and extracted the exostosis, with hardly any bleeding, and no injury to the neighbouring parts. My friend, Mr Joseph Lister, who was present at this operation, examined the growth removed microscopically, and, at my request, will now have the goodness to record the result of his observations to the Society. ARTICLE II.-Notes of the Examination of an Exostosis removed by (Read to the Edinburgh Medico-Chirurgical Society, Nov. 16th, 1853.) THE tumour was situated at the posterior and inner aspect of the bone, two or three inches from its upper end. Some idea of its general appearance may be gathered from figure 1 of the accompanying woodcut (see next page), which gives a lateral view of it of the natural size. It is seen to be of irregular form, presenting at its most prominent part several smooth rounded tuberosities: these were covered with cartilage, while the more circumferential parts of the tumour rose gradually from the normal level of the bone around, and were destitute of cartilage. The whole surface of the tumour was invested with extremely loose cellular tissue, which must have allowed very free gliding motion of superjacent parts; this cellular tissue adhered firmly, both to the cartilaginous and osseous portions of the surface. At a, a piece of the tumour had been broken off, exposing the cancellated texture of the interior, which in the deepest parts of the exostosis, was extremely loose, consisting of medullary substance traversed by very delicate spicula, which presented the microscopical characters of true bone (a lacuna with canaliculi from one of these spicula was shown in a sketch at the reading of the paper). In the circumferential parts of the tumour, which, as above stated, were destitute of cartilage, this loose cancellous structure exBut tended to within a very short distance of the surface, which was formed by a thin layer of compact, true osseous tissue. beneath the cartilaginous prominences there was a considerable thickness of compact substance, of a peculiar white aspect, too gritty and friable for true bone, and having a dark confused appearance under the microscope, with no definite structure; but after maceration in dilute hydrochloric acid presenting both to the naked eye, and under the microscope, the characters of cartilage. As a general rule, this calcified cartilage was present in greatest amount where the cartilage was thickest. Figure 2 exhibits part of a section made perpendicular to the surface of one of the prominences of the exostosis; a is the cartilage covering the surface, and is upwards of a line in thickness; the calcified cartilage b immediately beneath it was very dense, while at e the texture was looser, but even there, at a depth of five-eighths of an inch below the surface, cartilage cells showed themselves after maceration in acid. FIG. 1 is a lateral view of the exostosis: at a a piece of the tumour has been broken off, and the loose structure of the interior shows itself. FIG. 2 exhibits part of a section through one of the prominences of the tumour: a is the superficial cartilage; c is a portion of cartilage situated deeply, and surrounded on all sides by dense calcified cartilage, b and d; e is the deepest part of the calcified cartilage, of looser texture than the more superficial parts. FIG. 3 shows a section of a portion of the tumour at the line of junction of the calcified cartilage and the cancellous structure of the interior; the earthy matter has been removed by dilute hydrochloric acid: a is the cartilage with its cells changed by the process of calcification; b c is true bone (containing lacunae) lining the excavations in the calcified cartilage; d is part of a spiculum of the cancellous structure: e and fare spaces formerly occupied by medullary substance. The microscopical appearances of the superficial cartilage presented nothing very remarkable; the cells were larger than they are found in human articular cartilage, and many of them were of rather complex structure; they were much elongated at the free surface, where, indeed, it was difficult to distinguish them from the contiguous part of the investing cellular tissue; while in the deeper part of the cartilage they were more or less elongated in a direction perpendicular to the surface of calcification (a figure was shown representing one of these deeper cells). The matrix was homogeneous or faintly granular. The matrix of the calcified cartilage as seen after maceration in acid, was more granular, and the cells were rounder, and often surrounded with a broad pellucid ring, but the cells of the immediately adjacent part of the uncalcified cartilage assumed more or less of the same characters. The boundary between the uncalcified and the calcified cartilage was rendered very distinct by the circumstance that the matrix of the former was 1854.] STRUCTURAL EXAMINATION OF AN EXOSTOSIS. coloured brown by the action of the acid, while that of the latter generally remained colourless. At one spot, viz., at c in Fig. 2, a piece of cartilage existed at a considerable depth below the general surface of calcification, and surrounded on all sides by the dense pseudo-bone; this cartilage was extremely soft, and its cells remarkably large; one of them of circular outline measured inch in diameter; the nuclei also presented considerable variety of appearance, and complexity of structure. It might be supposed that these characters of the cells were connected with great rapidity of growth in this cartilage, and such may perhaps be the case; but the cells are not larger than exist in the central parts of costal cartilages. In the centre of a costal cartilage of a woman about sixty years old, I found cells very similar both in size and appearance, and it can hardly be supposed that any very rapid cell-development had been going on in that situation at such a period of life. The fact that the calcified cartilage was in some places looser in texture at its deep than at its superficial parts (e. g. looser at e than at b in Fig. 2) seems to indicate a change going on in the calcified cartilage by which it becomes converted into the loose cancellous structure of the interior. Examination of the deepest parts of the calcified cartilage under a low magnifying power, after the earthy matter has been removed by acid, shows that it is invaded by processes of the medullary substance of the cancellated tissue beneath it, which advance for a variable distance into its substance, and give a very irregular eroded character to its outline. The excavations thus seen to occur in the deep border of the calcified cartilage, are often lined with a thin layer of true bone containing lacunæ, which has, no doubt, been deposited subsequently to the formation of the excavations. Fig. 3 represents a small portion in this condition, where a is the deepest part of the calcified cartilage, b c is a layer of true bone lining the excavations e and f, which were formerly ocThe true bone is cupied by processes of the medullary substance; and d is part of one of the spicula of the cancellous structure. distinguished from the matrix of the calcified cartilage by having a higher refractive power than it. In the part where I first noticed this osseous lining of the calcified cartilage, it was almost universally present; very few of the excavations being even partially destitute of it. And the same appearance presented itself in the head of a metatarsal bone of a boy sixteen years of age, at the line of junction between the epiphysis and the cartilage which separated it from the shaft. Indeed, the resemblance between the two objects was exceedingly close, for the disposition of the cartilage cells in piles perpendicular to the surface of ossification, while present in the shaft of the metatarsal bone, was absent alike in the epiphysis, and in the exostosis; also the part of the cartilage that was immediately contiguous to the newly-formed bone of the epiphysis was evidently calcified, and closely resembled NEW SERIES.-NO. XLIX. JANUARY 1854. B the calcified cartilage of the exostosis, both in the condition of the cells and in the eroded form of its margin; the eroded edge, again, was almost universally lined with a layer of true bone exactly as in the exostosis, except that the layer was generally somewhat thicker. These facts appeared at first inconsistent with the idea of the layer of true bone having been deposited subsequently to the formation of the excavations, for that supposition implied that both in the epiphysis and in the exostosis, the process of excavation of the calcified cartilage had almost entirely ceased, or, in other words, that the conversion of the calcified cartilage into true bone was almost or altogether suspended; and this appeared particularly unlikely in the case of the exostosis, which was known to have been growing rapidly before its removal. The examination of the ossifying epiphysis of one of the bones of a calf's foot has, however, convinced me that the layer of true bone is deposited on the walls of previously existing excavations. The cells of the calcified cartilage are there seen to enlarge at the expense of the matrix as they approach the cancellous structure of the epiphysis, and at the same time to acquire a granular appearance, just like that of the rudimentary medullary substance with which the last formed areola are filled; and finally, they evidently form by their coalescence, the excavations in the margin of the calcified cartilage. Those parts of these excavations or areolæ, which are farthest from the perfect bone, and which have been last formed, are devoid of any osseous lining; but at a very short distance from their extremities they acquire upon their surface a thin layer of lacunated bone, which is seen to increase gradually in thickness at the expense of the cavities as they are traced nearer to the perfect bone. A further examination of the exostosis also showed that in some parts the osseous lining of the margin of the calcified cartilage was absent, while, on the other hand, there appeared at these parts, evidence of a change in the deepest cells of the calcified cartilage, like that observed in the calf's foot, viz., an enlargement of the cells, and a conversion of their contents into a granular substance previous to their coalescence to form the excavations. It thus appears that the process by which the calcified cartilage of the exostosis was converted into the cancellous structure of the interior, is essentially the same as what occurs in the ossification of the epiphysis of a metatarsal bone. The only difference between the two cases appears to be that in the ossifying epiphysis, the calcified cartilage is a very thin layer, while in the exostosis it is present in considerable thickness; but even in this particular there was not a constant difference between them; for the calcified cartilage varied much in thickness at different parts of the exostosis, and at some spots was, to the naked eye, absent or nearly so, even where cartilage existed on the surface. The great thickness of the calcified cartilage probably results, in part at least, from a want of energy in the process by which it is converted into the cancellated tissue, and accordingly it was just at |