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BELL SYSTEM TECHNICAL JOURNAL 



hyphae of the test-fungus which has been growing on a malt-agar 

 substratum. The bottles are then placed in an incubation room 

 (Fig. 5) at 26-28° C, customarily for a period of 24 weeks. At the end 



Fig. 5 — Incubator with tests in progress. 



of the test period the blocks, freed of adhering mycelium, are again 

 brought to equilibrium at a specified humidity, reweighed and the 

 pieces finally dissected to determine the loss of strength occasioned by 

 the attack of the fungus. 



