584 PERIOSTEOTOMY. 



point of the seton needle is forced and then withdrawn. 

 Into the free space thus made a curved knife is introduced : 

 the point of this knife is blunt, and the blade curves upward, 

 the cutting part being below. Some persons use a very- 

 diminutive blade, but the editor prefers rather a large instru- 

 ment, as being more under the command of the hand. 

 Having introduced this knife, he turns the cutting edge 

 downwards, and wdth it incises the enlargement, sending 

 the blade right through the periosteum, and also through 

 the substance of the exostosis, if it be not too solid for 

 the knife to penetrate. This latter fact is only to be as- 

 certained by actual experience, and no opinion formed after 

 an external examination can be of any value ; such being 

 much more the guess of a pretender than the judgment of 

 a surgeon. The age of the animal may be some guide, but 

 even this it is better not to depend upon too entirely. It 

 is true that young horses freely cast forth exostoses, 

 which aged animals mostly absorb ; but this rule, though 

 very general, has exceptions, and by no means is to be 

 absolutely depended upon. 



The enlargement being cut through, next take a seton 

 needle armed with a tape, and draw it through the channel 

 already made : tie a knot at either end of the tape, large 

 enough to prevent its being pulled through the opening at 

 either end, and the business is over. The affair is very 

 simple, and the horse may be at once let up. It is, how- 

 ever, in some cases, and only in some, of so much benefit, 

 that the horse being thrown " dead lame," gets up and 

 trots off quite sound. However, ere you adopt the ope- 

 ration, apprise the owner of the risk incurred, and that 

 it is by no means a certain cure. Leave the choice with 

 him, but be sure and tell him the openings made for the 

 entrance and exit of the seton commonly leave a blemish 

 behind them ; and where the seton travelled, often there 

 remains a thickening, which it may require months to 

 obliterate. 



The after part of the treatment consists in merely having 

 the seton daily moved to and fro : though some persons 

 apply an active blister all over the parts immediately in the 

 neighbourhood of the seton ; under the idea that the vesica- 

 tory renders the operation of greater efficacy, which how- 



