LAMENESS: ITS CAUSES AND TREATMENT. 327 



On the occurrence of the injury an effusion of blood takes place be- 

 tween the ends of the bone. The coagulation of the fluid soon fol- 

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

 then an excess of inflammation in the surrounding structure, which 

 soon spreads to the bony tissue, when a true ostitis is established, 

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

 organization, and of a certain exudation of plastic lymph, appearing 

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

 as 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, becoming vascular, is soon transformed into 

 cartilaginous, and in due time into bony, tissue. 



Thus the time required for the consolidation of the fractured seg- 

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

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

 by a bony plug or stopper, constituting the period of the provisional 

 callus. This is followed by the period of permanent callus, during 

 which the process of converting the cartilaginous into the osseous 

 form is going forward. 



The restorative process is sooner completed in the carnivorous than 

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

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

 within four weeks, but with the latter a period of from six weeks to 

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

 apparatus 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 practitioner, and especially when, from any cause, the 

 bony fragments have not been kept in a state of perfect immobility 

 and the constant friction has prevented the osseous union of the two 

 portions. Failures and misfortunes are always more than possible, 

 and instead of a solid and practicable bony union the sequel of the 

 accident is sometimes a false joint, composed of mere flexible carti- 

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

 that, first, the sharp edges of the ends of the bone disappear by 

 becoming rounded at their extremities by friction and polishing 

 against each other. Then follows an exudation of a plastic nature 

 which becomes transformed into a cartilaginous layer of a rough, 

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

 secreted between the segments thus transformed, instead of becoming 

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

 capsular sac, in which a somewhat albuminous secretion, or pseudo- 

 synovia, permits the movement to take place. Most commonly, how- 

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



