156 APPENDIX. [No. m.A. 



of tliis cliange from different situations ; ttey mostly show not only tlie 

 Haversian canals, bnt even tie corpnscules. 



We have next to examine adventitious bone ; whicli may be arranged 

 under tlie heads — reproduction of bone, growths from bone, and ossifica- 

 tions of other tissues. Of the former a piece of callus from a simple 

 fracture was examined, and was not found to differ in any respect from 

 true bone ; it had the cellules with their lines, and the Haversian canals, 

 precisely as normal bone. The same thing was noticed in a section of 

 callus from a compound fracture. The new bone after necrosis, or even 

 the necrosed portion, exhibited no diversity from this structure. The 

 reproduction of bone is particularly interesting, as the new deposit is 

 precisely the same as normal bone, with almost all the tissues ; the repro- 

 duced part widely differs from the normal tissue. 



Of the different gi'owths from bone, a piece was examined which had 

 been thrown out from two anchylosed vertebrae for additional strength, and 

 this presented the appearance of true bone. 



Hard bony exostoses were examined with exactly the same result. 



Ossifications may he divided into two classes— bone of cartilages, 

 and bone of other tissues. Ossifications of the thyroid and coracoid 

 cartilage in the human subject were examined, and both presented the 

 cellules, and the former the Haversian canals not at all different from 

 recent bones. 



The human trachea is not in general sufficiently ossified to show the 

 corpuscules of the natural size, for in partial ossifications large cells are 

 seen, but a section of a small part showed these cellules of the size natural 

 to bone. The trachea of the macaw, and the inferior larynx of the 

 widgeon, which are naturally bones, also present no difference from the 

 general appearance of bone. 



Examinations of the structures of the costal cartilages when ossified 

 were attended with like results. 



The ossification in the thyroid ligament was examined, which showed 

 here and there the cellules. 



The fibrous membranes when ossified do not generally exhibit this 

 structure : in fact, we may say never, unless they be connected with bone. 

 A portion of ossified tendon attached to bone was examined, which had 

 these cellules differing in no respect fi-om bone. 



A section of a fibrous tumour of the uterus was examined. This had 

 the fibres running in the osseous matter, but no cellules nor anything like 

 cellules could be discovered. 



Of the serous membranes, the pleura is sometimes ossified, but that 

 appears to be only a deposit of in-egulai- granules, and no structure could 

 be detected. 



The arterial tissue is frequently ossified, and then its appearance 

 is similar to that of the pleura; it displays a gi-anular mass and no 

 cellules. 



Thus we may state that ossifications ai-e of two kinds : first, that of 

 true bone, which, in a word, always exists when any enlargement of bone 

 in any way takes place, either as an ossification of the neighbouring tissues, 

 or in any other way. Secondly, ossification of the tissues not at all related 

 to bone, which presents nothing but a mass of granules. 



The stmcture of bone from a very old person was examined, which 



