460 EXAMINATION. [BOOK III. 



The extent of each sinus, and the course it pursues, 

 is denoted by the colour of the soft parts of the 

 foot being black or livid, or else but just tinged, 

 according to its virulence. In order to pursue this 

 examination more accurately, it will be necessary to 

 stop the circulation of the blood above, by tying a 

 ligature round the fetlock joint, whereby the skin 

 of the healthy parts below will appear white, and 

 thus more distinctly expose the nature of the si- 

 nuses. The pledgets that are to be introduced for 

 the destruction of the pipes may thus be selected of 

 a larger or smaller size, as the calibre of the sinus 

 appears greater or less ; as may also the quality of 

 the caustic application be made stronger or weaker, 

 as the virulence may require. 



Some hastily use the knife, and lay open the 

 pipes freely along their whole course ; and if it de- 

 scends to near the bottom of the foot, the coffin- 

 bone is usually affected with rottenness or decay, 

 usually termed caries. This they hesitate not to 

 scrape off, though, if the patient be of strong and 

 vigorous constitution, exfoliation will take place 

 without extending the operation so far. Indeed, it 

 seldom happens that more is required than to give 

 the disorder free vent at the coronet, whereby the 

 necessity of operating underneath is superseded ; 

 for it will be seen, that the ascent of the hoof- 

 making particles from the sole will bring away to 

 the orifice of the ulcer any offensive matters from 

 below ; and this process of nature effects the cure. 

 Whenever a sinus leads towards the back tendon, 



