FORMATION OF CALLUS. 75 



perfluous bony matter (the ring and the pin) being no longer 

 necessary, 'is absorbed, and the cavity of the bone with the 

 membranes of the latter is re-established.* In this case it will 

 be seen that the deposite of coagulating lymph into the cavity 

 of the fracture, corresponds with the mucous rudiments of the 

 foetal bone, and that the remaining phenomena of ossification are 

 the same. 



Some physiologists have attempted to give to the periosteum 

 the exclusive credit of the formation of callus: the view is erro- 

 neous, because experiments show, that even where the perios- 

 teum is stripped designedly from the fractured ends of bones, 

 they, nevertheless, unite, and the periosteum is restored when 

 the callus is formed. The probability then is, that all the blood 

 vessels (from whatever source they come) which penetrate the 

 organized coagulating lymph secreted between the fractured ex- 

 tremities, convey and deposite calcareous matter. 



The celebrated Bichat and some others, were of opinion, that 

 in every case of fracture where the ends of the bones are not 

 kept in contact, granulations spring up from the ruptured sur- 

 faces of the bone, and of its membranes; that these granulations 

 first receive into their interstices a soft gelatinous deposite, then 

 a cartilaginous one, and, finally, a calcareous one, by which the 

 bone is united. This process, however, is much more common 

 in compound fractures which suppurate, and may be considered 

 rare in simple ones. 



When the calcareous matter begins to take a place in a form- 

 ing callus, if the part be much moved, the process is arrested, 

 the blood vessels no longer deposite even if they carry calca- 

 reous materials, and an artificial joint is formed. The proper 

 period of restoration being once passed, the vessels sink into an 

 inactive state from which they have little or no disposition to 

 rouse themselves. Under these circumstances, Dr. Physick 

 proposed, many years ago, the introduction of a seton through 

 the cavity of the fracture, and the retaining of it there for a long 

 time, for the purpose of stimulating the vessels. The plan has 



* J. Hunter, paper by Mr. Home, in Trans, of Society for Improvement. Lon- 

 don, 1800. 



