VOL. XLIV.] PHILOSOPHICAL TRANSACTIONS. 245 



operations in surgery might he not have undergone, without the least probability 

 of having his malady found out, or obtaining a cure for it ? Probably many 

 desperate cases in surgery may arise from such accidents as this. 



Observations on the Spina Fentosa. By tfie late Claudius Amyand, Esq. F.R.S. 



N" 480, p. 193. 



What practitioners generally understand by the spina ventosa, is a caries in the 

 bone, from the extravasation of some sharp juices within it relaxing the tone of 

 the fibres, and swelling and increasing its bulk beyond the natural bounds. 



In this case, the humour, or extravasated juices, pent in the bone, works its 

 way out of it, through the external cortex, or into the joints, or both. By de- 

 tention it acquires an acrimony; and, like vinegar, and other acrid juices, it not 

 only relaxes the tone of the bony tubes, by mollifying them, but also, like a 

 caustic, it tears and lacerates them. At this time the bone swells, tumefies, 

 and spreads; and the sap flowing, running out through the lacerated tubes, 

 overspreads the surface, and adds to the tumefaction, as the liquid matter, 

 forming a callus, is indurated there. So that, when this happens at or near 

 the joints, the bones in contact are knit together, and the cariosity is in- 

 • crusted and covered with an exostosis, in as many places as the matter confined 

 within the bone, on breaking its cortex, will work its way out at. And thus 

 this distemper may be considered differently, as it happens to be in its different 

 stages. 



The alteration the bone suffers from the extravasated matter lodged within the 

 substance or cavities of the bone, in the first stage of a spina ventosa, becomes 

 the occasion of some exfoliation or detachment from it. As that matter acquires 

 a greater acrimony, the texture of the bone being relaxed, and the lamellae made 

 soft and yielding, the bone is enlarged in its dimensions; and, in the last stage of 

 it, in which the bone is carious, the corrosive matter destroys the continuity, as 

 it makes its way through the cortex, and into the joints. At this time imposthu- 

 mations appear in as many places as the matter can make its way out at. The 

 callous matter lodged under the periosteum, gradually ossifying, covers the bone 

 more or less with exostoses ; and the joints are stiflfened, by the extravasation and 

 induration of the sap flowing out of the bone there. 



The imposthumations that happen in the bone towards' the centre of long bones, 

 are always attended with additional mischief, as the working out of the matter 

 there meets with a greater resistance from their lamellae, which lie close, and are 

 compact; the exfoliations made in the first stage, and, as it were, in the begin- 

 ning of the spina ventosa there, being frequently confined and locked in by the 

 cortex of the bone, or some callous expansion on its surface. In the last stage of 

 this distemper in this place, the bone is usually perforated with large holes, tubu- 



