TREATMENT OF WOUNDS 39 



posed. A final surface dressing is necessary in 

 order to protect the cotton from the weather. 

 When the job is done the presence of the cotton 

 is barely discoverable. 



Not all dressings fit this process. Tar is apt 

 to harden at the edges and separate from the 

 wood. Paint would do fairly well, though it 

 would be very expensive. The asphalt com- 

 pounds work best. The first coat on the wound 

 can be of tar, asphalt being used to saturate the 

 fabric and for the final dressing. 



The manufacturers of pruning paints often ad- 

 vertise that their preparations contain nothing 

 which could be harmful to the tree. The writer 

 does not consider that an important point. None 

 of the materials commonly used is seriously in- 

 jurious to the wood. Tar usually kills back the 

 cambium an eighth or a quarter of an inch, but it 

 is normally killed as far back as that by drying. 

 Carbolineum often kills the cambium a little 

 farther, but is innocuous if it is kept an inch or 

 so from the edge of the wound. Don't choose 

 an expensive material over a cheap one for -the 

 sole reason that its analysis indicates that it con- 

 tains nothing which could possibly injure the cam- 

 bium. The cheap one may in practice be just as 

 good. 



All this discussion of wound dressings has been 

 necessary in order to make intelligible the brief 



