184 STRUCTURE AND ENDOWMENTS OF ANIMAL TISSUES. 



not at all lower in reality, the new structures actually formed being 

 as complex in the one case as in the other. It is nowhere, perhaps, 

 more remarkably manifested, than in the re-formation of nearly an entire 

 bone, when the original one had been lost by disease ; all the attach- 

 ments of muscles and ligaments, as well as the external form and inter- 

 nal structure, being ultimately found as complete in the new bone, as 

 they originally were in that which it has replaced. Much discussion 

 has taken place in regard to the degree, in which the different membra- 

 nous structures, that surround bone and penetrate its substance, par- 

 ticipate in its regeneration ; some having supposed the periosteum to 

 have the power of itself forming new bone, others attributing the same 

 power to the membrane lining the medullary cavities. It appears cer- 

 tain, however, that new osseous tissue may be formed in a great variety 

 of modes. It has been ascertained by Mr. Paget* that it may be pro- 

 duced through the intermediation of perfect fibrous tissue, either when 

 this previously existed as such (as the periosteum or interosseous mem- 

 brane), or when it has been newly formed by the fibrillation of the plastic 

 fluid effused as the material for reparation. The agency of the perios- 

 teum is seen in many cases of necrosis, in which that membrane has 

 been completely detached from the dead shaft, and new bone has been 

 generated from its interior. The ossification of a newly-produced fibrous 

 membrane is believed by Mr. Paget to be the ordinary mode of repara- 

 tion of fractures of the skull ; and it takes place in a manner essentially 

 the same as that of the original intra-membranous development of bone. 

 But new bone may also be formed, according to that most excellent ob- 

 server, by ossification of the fibrous tissue in its rudimental state ( 193). 

 In abnormal bone-growths, it sometimes appears as if the tissue had 

 been formed by the ossification of cells ; but more commonly the calci- 

 fication takes place in an earlier stage of tissue-production, that of the 

 "nucleated blastema," in which a granular osseous deposit is seen, which 

 gradually increases so as to form the lamellae of a fine cancellous texture, 

 at the same time inclosing the nuclei, which seem to occupy the places 

 afterwards to remain as the lacunae. It is seldom that the reparation 

 of bone takes place through the intermediation of cartilage; though 

 this is occasionally formed, rather, perhaps, in the lower animals than 

 in the human subject. 



308. The reparation of Bone, after disease, or injury, takes place ex- 

 actly upon the same plan as its first formation. A plastic or organiza- 

 ble exudation is first poured out from the neighbouring blood-vessels, 

 and this forms a sort of bed or matrix, in which the subsequent processes 

 take place. ^ At first all new bone possesses a minutely cancellous struc- 

 ture, much like that of the foetal bones in their first construction ; but 

 this gradually assimilates itself to the structure of the bones which it 

 repairs, its outer portions acquiring a more compact laminated struc- 

 ture, while its interior substance acquires wider cancellous spaces, and a 

 perfect medulla. When the shaft of a long bone of an animal has been 

 fractured through, and the extremities have been brought evenly to- 

 gether, it is found that the new matter first ossified is that which oc- 

 cupies the central portion of the deposit, and which thus connects the 



* Lectures on Reproduction and Repair, Medical Gazette, 1849. 



