OF THE BONES. 389 



610. The bony substance of new formation by which the 

 solutions of continuity in bones are united, is named callus.* 



When a long bone is fractured, besides the rupture of the 

 osseous substance, there takes place a rupture of the medullary 

 membrane, and commonly also of the periosteum, as well as of 

 the vessels of these membranes and of the bone. There re- 

 sults from these vascular and other divisions, a more or less 

 considerable effusion of blood around and in the interval of the 

 fragments. If the latter are kept in perfect contact, an agglu- 

 tination is presently effected between them and between the 

 other divided parts. There also supervene a swelling and dis- 

 tention of the soft parts that have been divided and of those 

 which surround them, which become compact like inflamed 

 cellular tissue. The marrow, at the place of the fracture, es- 

 pecially participates of this state. All these parts, and espe- 

 cially the agglutinating or organizable substance which dis- 

 tends them, successively ossify, and form at the exterior a bony 

 ring of greater or less extent, the thicknessof which diminishes 

 from the centre or from the seat of the fracture towards the 

 two extremities, and at the interior a fusiform bony mass. The 

 bone, however, of which the two fractured portions are thus 

 brought together, seems until now to be in no degree affected 

 by the changes which are taking place around it. It is only 

 from this period, and in proportion as these temporary external 

 and internal ossifications diminish and disappear by absorption, 

 that the agglutination of the fragments becomes converted into 

 a permanent bony union. 



Several pathologists, and in particular Bonn, Callisen, and 

 J. Bell, have contented themselves with observing the facts 

 without attempting to explain them. Numerous hypotheses, 

 however, have been proposed for the explanation of these re- 

 markable phenomena. Boerhaave, Haller, and Detlef, his dis- 



* Duhamel, Mem. de PJlcad. Roy. des Sc. Paris, 1741. Boehmer, De 

 Ossium callo, Lips. 1748. P. Camper, Observationes circa callum Ossium 

 Fractorum, in Essays and Observ. Phys. and Liter, vol. iii. Ediri. 1771. 

 Bonn, De Ossium Callo, &c. Amstel, 1783. Macdonald, op. cit. J. How- 

 ship, in Med. Chir. Trans, vol. ix. Lond. 1816. Breschet, Quelques Recher- 

 ches Hist, et Experim. sip k cal. Paris, 1819. 



