33S GENERAL ANATOMY. 



of a portion of bone that has been removed, have given rise to 

 the practice, in certain cases, of cutting out portions of diseased 

 bones in their state of continuity.* 



613. When the callus after having commenced is subjected 

 to repeated motions of flexion, twisting, distention, &c. it re- 

 mains flexible, as in the preceding case, or no union takes place 

 at all, and the ends of the bones remain in contact. This is 

 also the case when the ends of bones are separated by a slight 

 layer of muscular tissue. 



614. The broad bones have a stronger power of reparation 

 and reproduction than the long bones. After the bones of the 

 skull have been trepanned, a production is formed which is sel- 

 dom bony to the centre. After the same operation, if the se- 

 parated bony operculum is reapplied, it sometimes unites. t 

 The phenomena of reproduction are very imperfectly known 

 in the short bones. 



615. The separation of the epiphysesj takes place, in 

 young subjects, from mechanical causes, like fractures, and the 

 parts thus separated unite again by means of a similar callus. 

 Chronic inflammation of the joints of the long bones also some- 

 times, in children and young persons, causes the separation of 

 their epiphyses, which are not yet united. Both of these 

 kinds of separations are rare. A case of false joint, in conse- 

 quence of the fracture of the neck of the femur, has lately been 

 published as an example of separation of the epiphysis in an 

 adult. 



616. When an aneurismal tumour meets with a bone in 

 the course of its development, the latter is gradually destroyed 

 in the place which is in contact with the tumour, without any 

 residuum of its substance remaining. This destruction bears 

 the appellation of wearing of the bones. 



617. The morbid anatomy of the bones has already given 



* Roux, De la Resection, &c. Paris, 1812.Champion, De la Resection 

 des os dans leur continuity. Paris, 1815. 



f Merrem, Mmadversiones, quaedam, &?c. Giess. 1810. 



$ Reichel, De Epiphysium ab ossium diaphysi diductione. Lips. 1769. 



A. Bonn. Descriptio Thetauri Ossium Morbosorwn Hoviani. Amstel. 

 1783. Ed. Sandifort, Museum Anat. Acad. Lugduno~af.avae. Lugd. Bat. 



