198 ON THE COMPOSITION, STRUCTURE 



is well knowa that bone may be developed from fibrous tissue, a 

 lamiliar instance of this fact is witnessed in the case of the long 

 tendons of the foot of many birds, which, although consisting of 

 white fibrous tissue in the young bird, become converted into true 

 bone in the aged. Again, the bones constituting the vault of the 

 human skull are not developed through the medium of a cartilaginous 

 matrix, but have their origin in a fibrous membrane. I do not wish 

 to adduce instances of bony formations dependent upon pathological 

 changes ; these, although very numerous and striking, only testify 

 that such'^changesfmay take place in tissues consequent upon irrita- 

 tion and disease ; it is the physiological or healthy function of tissues 

 which now engages our attention, and not the abnormal change these 

 tissues may undergo consequent upon some morbid condition. 



Experiments have been made in reference to this subject upon 

 rabbits of various ages and under different sanitary conditions, and, 

 as we might expect, the most satisfactory results have been obtained 

 when the animal operated upon was young and placed under circum- 

 stances favorable to healtho The question for solution is, what is the 

 function of the periosteum in reference to the generation of bone, and 

 is it the formative organ. The following experiments afford a satis- 

 factory solution to the question : a portion of periosteum was detached 

 from the tibia of a living rabbit, one end remaining adherent to the 

 bone, the other end being securely attached by means of ligature to 

 the internal surface of the skin ; the wound being closed, union of 

 the divided integument was speedily accomplished. Three or four days 

 after the operation the periosteum became perceptible to the touch, 

 had increased in size and firmness, becoming daily more and more 

 distinct ; seven weeks after the operation, having killed the animal, 

 the detached portion of periosteum was found to have developed a 

 piece of bone — in form corresponding to the position in which the 

 periosteum had been placed — that is to say, somewhat circular. 

 When a precisely similar operation was performed upon an old rabbit, 

 (five years old) no such results were obtained ; but, on the other 

 hand the wound suppurated, a serous pus or rather a pus resembling 

 tubercular matter was effused, without the slightest discoverable 

 attempt towards the formation of bone. "We may therefore infer that 

 the osteorgenetic power diminishes with age — and also that any form 

 may be given to the bone by simply placing the detached periosteum 

 in the position we desire the future bone to assume. 



