166 MASS. EXPERIMENT STATION BULLETIN 170. 



when applied to reservoirs, ponds, etc., for cleaning out objectionable 

 growths of many kinds, even when used at 1 to 1 ,000,000 parts or at 1 to 

 10,000,000 i^arts; while to be effective against the common blue mold, 

 Penicillium, which is often found in the wood of dead trees, it requires 

 a solution of about 1 to 30, or several thousand times stronger. 



In the disinfection of wood tissues the following points should be con- 

 sidered. The disinfectant should be capable of penetrating wood tissues. 

 An oily substance, which has more penetrating power, is far better adapted 

 to this purpose than a watery solution. The substance should be only 

 slightly volatile and should keep its original form, or at any rate its 

 antiseptic properties, indefinitely. Copper sulfate, corrosive sublimate, 

 formalin, lime and sulfur, and Bordeaux mixture have been used as dis- 

 infectants and preservatives in the 

 treatment of tree cavities, scars and 

 wounds, and while all of the above- 

 named substances have specific disin- 

 fecting properties it does not neces- 

 sarily follow that they are adapted to 

 wood tissues. 



The above-named substances pos- 

 sess limited powers of penetration, 

 and have little or no permanent anti- 

 septic value when applied to tree 

 wounds. Coal tar is also objection- 

 able because of its lack of penetrating 

 l)ower, and because it loses its fungi- 

 cidal value as it becomes hard. A 

 thick, nonpenetrating material applied 

 to wood is not only of no value, but 

 becomes an injurious agent, as shown 

 by the treatment of shingles on roofs. 

 The old practice of tarring roofs 

 simply induced decay because the tar 

 coating conserved moisture in the sliingles, and decay followed more 

 rapidly than in the untreated shingles. Coal tar, however, is useful in 

 covering surfaces previously treated antiseptically. In fact, the use of 

 creosote followed by coal tar constitutes one of the best scientific treat- 

 ments known, especially for exposed wounds. On the other hand, paint 

 which contains plenty of oil is valuable, as has been proved by long 

 years of experience. It lacks durabiUty however. 



Shellac dissolved in alcohol and applied to wounds is serviceable for 

 filling the pores of wood and preventing decay, and hence is of some 

 value as a wound dressing. Gas tar and liquid asphaltum are also some- 

 times used to cover wounds, and there are specially prepared paints and 

 other substances for use as wound dressings. Even common painter's 

 oil is excellent for the treatment of wounds, as it prevents checking of 



Fig. 27. — Inferior mechanical work. 

 Iron band too low for best support, 

 and also causing girdling. 



