ANIMAL GRAFTS AND REGENERATIONS. 239 



comes unfit for ossification. Robin and Dubreuil have also 

 proved that bony tissue may be formed without any carti- 

 lage existing beforehand, without any intervention of mem- 

 brane, and may proceed directly from a bone deprived of 

 membrane. These discoveries, without taking from the peri- 

 osteum the evident share which it has in producing renova- 

 tions of bone, give a conception of its mechanical action 

 which differs from that which physiologists had admitted. 

 They prove that really, in experiments of the kind tried by 

 Duhamel, Heine, Flourens, it is bone which produces bone, 

 as the severed nerve produces nerve. The cartilaginous 

 or bony layer adhering to the periosteum is hi fact noth- 

 ing else than bone in process of formation ; and whenever, 

 whether by means of the periosteum or by means of an 

 irritation, the reproduction of a certain quantity of bone 

 is procured, it is because, in the first place, conditions fit 

 for the production of cartilage have been brought about. 

 These remarks will allow us to understand and to give a 

 rapid estimate of the value of surgical methods founded on 

 the knowledge of these facts. 



Diseases of the bones are numerous. Independently 

 of those cases in which they are directly injured by pro- 

 jectiles, they are liable to inflammations, tumors, and decay 

 of every kind. These diseases are slow, in proportion to 

 the slowness of vital elaborations in those organs, but they 

 are not the less destructive, and they always end by bring- 

 ing about a more or less considerable corruption of the 

 substance of the bones. It is then necessary that the mat- 

 ters given off by the diseased bone should be cleared away : 

 the mortified portions must be got rid of. The limb very 

 soon swells, and becomes painful. Pieces make their way 

 through the skin, suppurations are set up, and, if art does 

 not interfere, the patient is led by exhaustion to a miser- 

 able death. To this concourse of evils surgery opposes 

 difficult operations. It cuts deep openings, it loosens the 



