OF THE SHAFT OF A LONG BONE. 73 



are prevented from closing by the continued flow of the pus. 

 The situation of cloacae is determined by circumstances in the 

 death of the old, and kept open by the continued flow of the 

 secretions of the new shaft. 



As, therefore, it has been found impossible to separate the peri- 

 osteum in living animals, without detaching shreds of bone along 

 with it ; as in necrosis of the shafts of long bones, portions of the 

 old osseous texture may be detected in the periosteal sheath 

 opposite ulcerations of the dead shaft ; and as consistent with 

 what is at present held regarding the powers of capillary vessels, 

 and the origin of the textures, we are compelled to assent to the 

 doctrine that periosteum does not possess an independent power 

 of forming osseous substance. 



The participation of the periosteum in the office of regenera- 

 tion an important principle in surgery is not denied in this 

 conclusion. 



J. G. 



