Licence: Public Domain Mark
Credit: A manual of pathological anatomy (Volume 3-4). Source: Wellcome Collection.
Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)
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![_ It appears as if it had been planted on the surface of the bone from without: in general it is a plane convex nodule, the margin of which is abrupt, and often separated from the bone beneath by a furrow. This furrow is generally narrow, sometimes being but just perceptible, and about the thickness of a hair; but frequently it is deep, and forms a fissure between the tumor and its basement. It gives the exostosis the appearance of having been glued on, or of sitting, mushroom-like, on a very short stalk. Not only is this exostosis in all cases compact, but it often exceeds in density the bone from which it springs: it is then known as the ivory exostosis. It is especially liable to be formed on bones which are them- selves indurated. It is compact from the very first; and grows in such a way that the layers which are added to it always at once become as dense as ivory. Neither the most superficial and most recent strata, nor the smallest of those exostoses, which form near larger ones, even though.no larger than hemp-seed or a lentil, is ever seen to contain any spongy structure. New layers and old, large exostoses and small, are equally dense and hard. When they are minutely examined, the number of peripheral lamellae is found to be very considerable; and the corpuscles lying amongst them are long. The Haversian canals are small and far apart, and many of them are surrounded by a distinct and completely defined (vb'llig abgeschlossenen) lamellar system. With regard to the corpuscles, we find large tracts without any of them, while at other spots they are clus- tered together in dense groups. The number of these exostoses occurring in one person, and even on the same bone, is sometimes very considerable; especially if the very small ones, which are easily overlooked, be also enumerated. I have met with them almost exclusively on the skull, where, like induration, they do, in fact, most frequently occur; but they are likewise observed on the long bones, and on the bones of the pelvis. They vary in size from that of a flattened hemp-seed or a lentil, which is scarcely perceptible, to that of a walnut, or a hen's egg, and even to greater dimensions. Their most common size ranges between that of a pea and that of a hazel-nut. While their usual form is that of a plane convex nodule, their surface, whether even or uneven, is always smooth and polished. If they grow beyond the ordinary size, they become round, or oval, or, as they gene- rally rather increase in length, they form a more or less cylindrical, horn-like projection. There is another form which occurs with them on the inner table of the skull near the frontal crest: it has a peculiar humifuse1 character, or the appearance of a convoluted wreath. The color of these exostoses is white or yellowish-white,—whiter than that of the bone to which they are attached. As we cannot associate exostoses, in respect to their cause, with the various inequalities and nodules that occur on bones from constitutional disease, especially from syphilis, the occasion of their origin must be 1 [Humifuse—growing parallel to the surface, but attached only at its point of origin, like the stems of plants which creep along the ground without taking root. (Palmer's Pent. Diet.)—Ed.]](https://iiif.wellcomecollection.org/image/b21151106_0111.jp2/full/800%2C/0/default.jpg)
