162 THE OCEAN FLOOR 



gram of the Swedish Deep-Sea Expedition, but the 

 investigation had to be abandoned for lack of time and 

 the requisite instruments. Otherwise, a special attempt 

 would have been made to find out whether bacterial 

 action is involved in the growth of the manganese 

 nodules, as has been suggested by a Russian scientist. 



The Danish expedition with the "Galathea" was 

 more fortunate, as they were well provided with re- 

 sources for collecting and cultivating bacteria from the 

 sediment in great depths and moreover had elicited the 

 cooperation of the world's foremost expert on marine 

 bacteria. Claude ZoBell of Scripps Institution of 

 Oceanography. The following is a brief summary of 

 ZoBelFs report on his investigations on board the 

 "Galathea," which he had the kindness to show me in 

 manuscript shortly after his return to Scripps.^ 



Microscopic examination of a sample of mud raised 

 to the surface from a depth of 7,200 meters in the Java 

 Trench revealed the presence of more than one million 

 bacteria per gram. Measured amounts of the mud were 

 inoculated into tubes with a nutrient medium. Little 

 or no growth was observed at ordinary atmospheric 

 pressure or at 30° centigrade, but in tubes incubated at 

 3° centigrade and placed in steel cylinders with a 

 hydrostatic pressure of 700 atmospheres, equivalent 

 to a water depth of about 7,000 meters, from ten to a 

 hundred times more bacteria were reproduced. Also, 

 many more bacteria were demonstrated in bottom 

 deposits than in the overlying water. In mud taken from 



