126 THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1953 



ing value of the substance tested. Other factors, such as leaching, vola- 

 tility, chemical stability, penetrability, cost, cleanliness, etc., must all 

 be considered in the final evaluation of a wood preservative." 



With respect to the European wood block test, he felt that 



" . . . until more confidence can be placed in the even distribution of the 

 preservative in the test block (s) their use will be greatly limited." 



He has maintained his arguments with a high degree of consistency in 

 later papers, and they have unquestionably influenced American thought 

 on laboratory procedures and their practical application. 



The Petri dish method adopted as a possible American standard pro- 

 cedure at the 1929 St. Louis meeting followed closely the techniques that 

 had been developed and published by Humphrey et al.,^^ Batemen^ and 

 Richards.^ Bell Telephone Laboratories made an intensive study of the 

 Petri dish method during this period. The data obtained were never 

 organized for publication since it was felt that the required evaluation of 

 toxicity and permanence of toxicity of preservatives could not be ob- 

 tained by the Petri dish test. 



European workers would accept neither the Petri dish test method nor 

 Madison 517 as the test fungus. In 1931, about a year after the Berlin 

 conference, and four years before Liese et af ^ reported on the task force 

 development of the agar-block method, A. Rabanus of the I. G. Farben- 

 industrie Aktiengesellschaft, Germany, published his ''Die toximetrische 

 Priifung von Holzkonservierungsmitteln" (Toximetric testing of wood 

 preservatives).^^ A somewhat expurgated and amended translation of this 

 paper was presented to the American Wood-Preservers' Association in 

 1933. In the writer's opinion much of the force of the Rabanus argument 

 was lost in the translation. The emphasis on the relative merits of the 

 agar toximetric test and of the agar-block test was considerably diluted; 

 and the cautiously guarded but nonetheless positive philosophy on the 

 possibilities of using the results of agar-block tests in actual wood pre- 

 serving practice was made water thin. 



Apparently there was an understanding that subsequent to the 1930 

 conference in Berhn^^ tests by the agar-block method would be run in 

 the United States. For this project samples of creosotes as well as Scotch 

 pine wood blocks were sent to a number of workers; but to the writer's 

 knowledge no treated blocks were ever tested, or if they were no results 

 were ever published. At Bell Telephone Laboratories some of the un- 

 treated Scotch pine blocks were put through preliminary trials with the 

 Kolle flask technique,^^^ and also a considerable number of plate and 

 flask agar toxicity tests were run with the two sample creosotes. The 

 inconsistency of the results — as far as translation to practical wood 



