IgO PROFESSOR SYME ON THE POWER OF THE PERIOSTEUM 



the periosteum, and different sides of the question are maintained by teachers and 

 writers in this as well as other schools of medicine. As the point in dispute is not 

 merely a matter of curiosity, but one of great practical importance, it is very de- 

 sirable that the truth shoiild be ascertained. It would detain the Society too long 

 were I to shew how the different opinions on this subject may influence the prac- 

 tice of surgery; and I shall, therefore, proceed to state the considerations which 

 have completely satisfied my own mind, and are, I think, sufficient to satisfy any 

 one who is open to conviction, that though Duhamel was misled into many eiTors 

 by the Mse analogy which he supposed to exist between wood and bone — in re- 

 gard to the mode of their natural formation — the periosteum nevertheless does pos- 

 sess the power of producing new osseous substance in certain conditions of disease. 



The well-knoAvn and often-repeated experiment of Troja, which consisted in 

 perforating the cavity and destroying the maiTow of a bone, so as to kill it and 

 cause the formation of a substitute in the form of a shell sun-oundiug the old one. 

 was devised in imitation of a process which not unfrequentl}' occurs spontaneous- 

 ly in the human body. In this disease, which has been named Necrosis, a portion 

 of the old bone "dies, and becomes surrounded by a new one. There is an example 

 of this on the table, in which the tibia, or principal bone of the leg, has been thus 

 affected. The new shell is of a larger size and more irregular form than the old 

 one, which may be seen through a number of cu-cular apertiu-es lying a prisoner 

 within this structure, intended by Nature to serve as a substitute for it. Those 

 who deny the ossific power of the periosteum, maintain that in all such cases, 

 whether resulting from injiuy pm-posely infUcted with the view of experiment, or 

 proceeding from diseased action, a portion of the old bone remains alive, and serves 

 as the germ of a new one ; that, in short, the formation of the new bone is sim- 

 ply an expansion or growth fi-om the remnant of the old one, and that if merely 

 the extremities of the bone affected remain alive, they will prove sufficient for ge- 

 nerating the substitute shell. 



It is difficult to reconcile this explanation with the rapid gi-owth and uniform 

 thickness of the new bone ; since, if its formation proceeded fi-om the extremi- 

 ties, the process should be slow and progressive towards the centre ; but there is 

 another objection stiU more conclusive against it. If the new bone is formed by 

 a portion of the old one that remains alive, then the removal of a part by mecha- 

 nical means should be supplied fi-om the same source. But in all the cases where 

 this has been done, either in the way of experiment or for the cure of disease, the 

 loss of substance, unless of small extent, has been found imperfectly repau-ed. 

 For instance, after the operation of trepanning the skull, the apertiu-e in the bone, 

 though it becomes diminished in extent, is not altogether obliterated, and the 

 newly-formed bone is not only smaller than the portion removed, but also thin- 

 ner, as may be seen from the specimens before me. 



