494 THE BELL SYSTEM TECHNICAL JOURNAL, MARCH 1953 



of preservative needed in the upper, or above ground section, of thin 

 sap wood poles. 



The work of Tippo and his associates represents one phase of an ex- 

 tensive set of experiments in which large (6 x 5 x J^ inch) and small 

 (3 X 5 X J^ inch) specimens are made up to simulate a butt-block as- 

 sembly, and exposed to the attack of certain critical fungi by adding to 

 the block assembly another inoculum block (3 x 5 x % inch) that has 

 been thoroughly infected. The assembled units are kept in a warm and 

 practically saturated atmosphere until the reaction of the fungus to the 

 different preservatives can be determined. This work is being expanded 

 in view of the importance of minimizing decay in wooden ships. 



The point to be made here is that Verrall's tests and Tippo's tests 

 should be evaluated carefully before the service test program is broad- 

 ened extensively. 



OTHER OBSERVATIONS 



Some of the results of Suolahti's interesting studies"^ on the influence 

 of Avood at a distance on the intensity and direction of growth of fungus 

 filaments (mycelium) have been confirmed by preliminary experiments 

 at Bell Laboratories. Small sterilized southern pine sapwood blocks en- 

 closed in either test tube or Petri dish cultures exert a positive pull on 

 the filaments that is effective over a distance of several centimeters. The 

 growth of the mycelium is more luxuriant, and the filaments are definitely 

 drawn in the direction of the wood. Without attempting any interpreta- 

 tion of the significance of this phenomenon one may be permitted to 

 point out that such studies strongly support the very great desirabiHty 

 — if not the necessity — of using wood in any studies directed toward 

 evaluation of wood preservatives. 



In view of the nearly forty years of prior work both here and in 

 Europe, in which it was definitely established that certain higher fungi 

 were the principal causes of decay in wood, it is hard to see why Weiss^^ 

 spent so much time and such careful work on trying to test wood pre- 

 servatives by using bacteria as his bioassay agents. Following the pre- 

 sentation of his paper before the Society of Chemical Industries in 1911 

 some of Weiss's critics pointed out that his methods were unrealistic as 

 far as oil preservatives were concerned, one of his commentators suggest- 

 ing that the proper approach to the problem of preservative evaluation 

 was to test treated and untreated wood, (unsterilized and sterilized) under 

 conditions favorable for fungus growth. 



Tamura in 193l"^ used an assembly of two pieces of treated wood 



