PRACTICAL TRKK SURGERY 



725 



outside-ground socket-handled gouges 

 (one with a curved cutting edge of 

 about three-fourths of an inch and the 

 other, perhaps, one and one-half 

 inches), a chisel, a mallet, a knife, and 

 an oilstone are sufficient for ordinary 

 work. The gouges, chisel, and knife 

 should never be used near the cambium 

 when they lack a keen edge, as dull 

 tools will injure it. In cutting out deep 

 cavities, longer interchangeable handles 

 for the gouges may be necessary. 



EXCAVATING. 



Usually an old decayed spot may be 

 partially or wholly covered by a new 

 growth of wood and bark at the edges 

 and the visible decayed area be small 

 as compared with that which is hidden 

 (Plate No. 1, figures -i and G). In 

 such cases it is usually necessary to en- 

 large the opening with the gouges and 

 mallet in order to make sufficient room 

 in which to use the gouges in the in- 

 terior. This opening should be suf- 

 ficiently long to reach all the decayed 

 and diseased heartwood with little or 

 no additional injury to the tree. 



If the decayed and diseased wood ex- 

 tends some distance above or below the 

 external opening, it is a common prac- 

 tice to cut one or more holes above or 

 below the main opening in order to 

 facilitate the removal of the diseased 

 wood (Plate No. 3, figure 1). This 

 results in one or more bridges of wood 

 and bark spanning the long interior 

 cavity. This practice is of doubtful 

 value, partly because it is often impos- 

 sible to see whether the diseased wood 

 has been entirely removed from the 

 under side of the bridges, but mainly 

 because there is a strong tendency in 

 most trees for the bark and sapwood of 

 the bridges to die and decay as a result 

 of severing the sap-conducting tubes 

 both above and below. If the holes 

 are pointed above and below, there is 

 less trouble from this source. A prac- 

 tice that permits a more thorough clean- 

 ing out of the cavity is to make a nar- 

 row opening, pointed at both ends and 

 sufficiently long to include all the dis- 

 eased wood. This often extends some 

 distance above and below the visible dis- 

 colored area. 



The most important feature of this 

 stage of the work is to remove all the 

 diseased and insect-eaten wood (Plate 

 No. 3, figures 2 and 3). This excavat- 

 ing must continue on all sides of the 

 cavity until sound, uninfected wood is 

 reached (Plate No. 1, figure 4). All 

 discolored or water-soaked heartwood 

 should be removed, as this is the region 

 in which the rot-producing fungus is 

 most active. In decayed areas of many 

 years' standing there may be only a 

 thin shell of uninfected wood around 

 the cavity (Plate No. 1, figure 6), hi 

 which case there is danger of the tree 

 being broken by storms unless braced 

 or guyed. 



The bottom and all other parts of 

 the cavity should be so shaped that if 

 water were thrown into the cavity it 

 would promptly run out and none re- 

 main in any hollow. 



UNDERCUTTING. 



Another important point to be borne 

 in mind in shaping a cavity that is to 

 be filled is to have the sides undercut if 

 possible, so as to hold the filling firmly 

 in place. Care must be taken, however, 

 not to have the wood at the edges of 

 the opening very thin, as this promotes 

 the drying out of the bark and sap- 

 wood at these points. Ordinarily the 

 edges should be at least three-fourths 

 of an inch thick ; an inch and a half 

 would be better (Plate No. 1, figure 4 

 and Plate No. 4, figure 1). 



Great care must be exercised in 

 working around the cambium, and all 

 cutting tools must be kept very sharp. 

 The final cutting along the edges of the 

 bark and sapwood can usually best be 

 made with a very sharp knife. This 

 cutting must be followed immediately 

 by a coating of shellac, which should 

 cover the edges of both bark and sap- 

 wood. 



BOLTING. 



Before cementing a long cavity it ij 

 advisable to place through it one or 

 more bolts, so as to hold the wood and 

 cement more firmly in place. A cavity 

 two feet or less in length will not usual- 

 ly require a bolt, but long cavities, 

 as a general rule, should be bolted every 



