VARIOUS TYPES OF CAVITIES 161 



mouth of the hole should be trimmed up and 

 cleared of ingrowing callus. 



The filling material to use in such a cavity de- 

 pends upon its shape and upon its position in the 



Deeply decayed knot-hole and the same excavated and filled with 

 asphalt 



tree. If it is in a large trunk where there is likely 

 to be but little strain on the filling, cement will do 

 very well, after, of course, a thorough dressing 

 with some form of asphaltum. If, however, the 

 hole is in a limb, and at a point where there is con- 

 siderable twist and bend, cement will not do, for 

 it will break up and perhaps be forced out of 



