EXPERIMENTS INITIATED IN 1909 45 



with low powers of the microscope. I have little 

 doubt but that in the early months of 1910 I failed 

 to find organisms in several of the tubes because 

 I trusted to being able to detect them with too 

 low a power. Up to April 30th I had been habit- 

 ually searching for organisms with a one-inch ob- 

 jective and a No. 6 compensation eyepiece. But 

 on that day I began to adopt the more laborious 

 method of diligently searching through the whole 

 sample of the deposit with a quarter-inch objective 

 and the same eyepiece; and the result has been 

 that organisms have been found in every one of 

 the remaining thirty-seven tubes whose contents 

 were examined. In several cases the organisms were 

 so minute that they would almost certainly have 

 escaped observation had I been searching only 

 with the low power. Still, in part this increased 

 number of positive results has doubtless been due 

 to the fact of the longer times that had elapsed 

 after the heating process before the tubes were 

 opened. Thus, out of the total number of 105 

 trials, in this series of experiments, with hermetic- 

 ally-sealed tubes heated to temperatures ranging 

 from 100 C. to 135 C., there have been sixty- 

 six positive results; while in eighty-five of these 

 trials, in which the tubes had been heated from 



