CRITERIA AND METHODS 127 



avoided. He reduced the injury from drying by covering 

 the wound with adhesive tape, but in comparing the two I 

 have found that the adhesive tape is less efficient than 

 paraffin. Since it seems probable that the loss of water 

 may be effectively checked by the tape, it may be the 

 abnormal aeration or the presence of microorganisms in 

 the space below the tape that makes this method of protec- 

 tion inferior, Drinkard and Ingham (1917) found that 

 waxed paper or adhesive tape were fairly effective in pre- 

 venting the drjdng out of ring wounds and in promoting 

 their healing. Various paints, tar, and even grafting wax 

 that was softened with linseed oil all proved injurious. 

 Healing beneath the waxed paper was still further pro- 

 moted if the ring wound was first sterilized with a saturated 

 solution of saUcyhc acid or 10 per cent creohn. Other dis- 

 infectants used were less effective. The fact that healing 

 was better when evaporation was prevented and fungus 

 growth eliminated by disinfection, would indicate that 

 growth of microorganisms may have injurious effects. No 

 tests were made in which warm paraffin was directly 

 applied to the wound. Wee vers (1928) assumed that 

 cocoa butter was better than paraffin because it could be 

 applied at a lower temperature, but he made no experi- 

 mental comparison. Since its melting point is so low, it 

 may be preferable to paraffin in certain cases. Mason 

 and Maskell used vaselin to protect ring wounds. Though 

 I have made no comparative tests with ring wounds, I did 

 find that twigs coated with vaselin were killed, while 

 similar twigs coated with melted paraffin were uninjured 

 (Curtis, 1918). Anderssen (1929) states that ''Even 

 though the ring of bark is removed without directly injur- 

 ing the tracheae, the wounding and exposure to the air is 

 sufficient to cause injury resulting in the clogging of such 

 tracheae with air and gums." But he overlooks the 

 possibility of protecting the exposed tissues and thus pre- 

 venting such clogging. 



Summers (1924) has made measurements of water loss 

 from ring wounds and partly explains the effects of ringing, 



