lameness: its causes and treatment. 327 



On the occurrence of tlie injury an elTusion of hlood takes place be- 

 tween the ends of the Ixme. The coajruhition of tlie Ihiid soon fol- 

 lows, and this, after a few days, underjjoes absorption. There is 

 then an excess of inflauiiuation in the surroundinjj .structure, which 

 S(»on spreads to the bony tissue, when a true o.stitis is established, 

 nnd the compact tissue of the bone becomes the seat of a new vascular 

 oriifanization, and of a cei-tain exudation of plastic lyuiph, appearinj^ 

 between the periosteum and the external surface of the bone, as well 

 us on the inner side of the medullary cavity. After a few days the 

 ends of the bone thus surrounded by this exudate become involved 

 in it, and the lymph. bocomin<; vascular, is soon transforujed into 

 cartilaginous, and in diu' tiuie into bony, tissue. 



Thus the time leciuiicd lor the consolidation of the fractured seg- 

 ments is divisible into two distinct periods. In the iirst they are sur- 

 rounded by an external bony ring, and the medullary cavity is closed 

 by a bony plug or stoppei-. constituting the ])eriod of the provisional 

 callu.s. This is followed l)y the period of permanent callus, iluring 

 which the process of converting the cartilaginous into the osseous 

 form is going forward. 



The restorative process is sooner completed in the carnixorous than 

 in the herbivorous tribes. In the former the temporary callus may 

 attain suflicient fineness of consistency for the careful use of the limb 

 within foin- weeks, but with the latter a period of fiom six weeks t<» 

 two months is not too long to allow before removing the supporting 

 nppai'atus from the limb. 



This, in general terms, represents the fact when the resources of 

 nature have not been thwarted by untoward accidents, such as a want 

 of vigor in the constitution of the patient or a lack of skill on the 

 part of the practiti(mer. and especially when, from any cause, the 

 bony fragments have not been kept in a state of perfect immol)ility 

 and the constant fi-iction has prevented the osseous union of the tw<» 

 portions. Failures and misfortunes are always more than ])ossibh'. 

 and instead of a soli<l and ])raoticable bony union the sequel of the 

 accident is sometimes a false joint, comj^osed of meiv flexible carti- 

 lage, a poor p.seudarthrosis. The explanation of this appears to be 

 that, fii-st. the sharp edges of the ends of the bone di.snppear by 

 l)ecoming rounded at their extremities by friction and polishing 

 against each other. Then follows an exu«lation of a plastic natnre 

 which becomes transformed into a cartilaginous layer of a rough, 

 articular aspect. In this bony nuclei soon appear, and the lymph 

 secreted In'tween the segments thus transformed, instead of becoming 

 truly ossified, is changed into a sort of fibrocartilaginous pouch, or 

 capsular sac. in which a somewhat albiuninotis s<>cretion, or j^seudo- 

 synovia, ])ermits the movement to take jdace. Most commonly, lutw- 

 ever, in our animals, the union of the bonv fragments is obtained 



