Parker. ] 98 [November 6, 
first, to secure a perfect sealing of the flask; second, to know the 
exact nature of the infusions inclosed. To secure the first object I 
determined to seal the flasks first and then expose them to heat after 
being sealed. To this end I adopted the following process. Such 
substances were used as are regarded most favorable for the develop- 
ment of life. These were properly prepared by maceration in warm 
water for from one to two and a half hours. The infusions were then 
filtered three times successively through different pieces of filtering 
paper; portions of the filtered infusions were then placed in flasks 
and carefully sealed with spirit lamp and blow pipe. A strong copper 
vessel} was prepared capable of enduring a pressure of one hundred 
and fifty lbs. to the square inch, in which to boil the infusions. In this 
vessel were two unions; the coupling of one of them being closed at 
its bottom was filled with fish oil in which was inserted a thermom- 
eter; through the other union the sealed flasks containing the pre- 
pared infusions were introduced. ‘The copper vessel was then nearly 
filled with water. Proper precautions: being taken for the exclusion 
of air a spirit lamp was applied, and the degree of temperature noted 
as indicated by the thermometer. In order to keep my judgment un- 
biassed during these experiments while opening and examining the 
flasks, and also to be able to determine whether any changes had 
taken place in the fluids after their enclosure and heating, I adopted 
a peculiar system of recording the experiments. A few drops of each 
infusion as prepared for the flask were placed upon a slide having 
a concave cell, and a one-tenth immersion lens made by Wales was 
focussed to the bottom of the cell, and the contents carefully ex- 
amined every few minutes for an hour. A careful record of its con- 
dition was entered in a book for the purpose. The flasks were num- 
bered and each number entered in connection with the recorded 
character of each flask. When afterwards the flasks were opened 
and scrutinized, another record was made in another book. It is 
important to state that the first record was not referred to, nor was a 
comparison made between the two records until all the investigations 
were completed. Consequently the contents of the flasks and the 
nature of the infusions were unknown at the time of their examina- 
tion. By this system of record and comparison the changes in the 
fluids, if any occurred, could be easily discovered. For, if the first 
record showed a special organism, say, rod-like bacteria, existing in 
any infusion to the exclusion of all other forms of life, and if after a 
lapse of time sufficient for all the possible changes to take place of 
1 See plate 1. 
