1878.] O7 [Parker. 
instance that where living organisms existed in the infusions before 
boiling they were found dead in the infusion after it bad been sub- 
jected to boiling heat ; thus establishing the fact that while these or- 
ganisms were killed by the heat of boiling water they resisted dis- 
integration, and their remains were found in the infusions after boil- 
ing. J next prepared other infusions in the same manner as before, 
macerating the substances in warm water, and then filtering, boiling, 
and sealing them in flasks. But I now, after maceration, subjected 
a part of each infusion to microscopic examination before boiling; 
and after boiling, another portion was examined with the microscope, 
while the remainder was placed in flasks boiled with the flame of a 
lamp and sealed during ebullition. In all such experiments, when 
living bacteria were found in the infusion before boiling, I found dead 
bacteria after boiling, and also in the flasks when after an interval 
ranging from a few days to several weeks they were opened ; showing 
that the bacteria had developed during the maceration, and were de- 
stroyed during the heating process. In a great number of these 
flasks living organisms were found upon opening them, and these 
were found in flasks containing infusions in which no life was found 
in the first examination. In all such instances the questions arose, 
did the organisms originate in the infusions in the flask ? or did 
air enter during or after the process of sealing the flask which con- 
tained the germs that afterward developed into life? In experiments 
carefully made with a view to determine this question, I found it ex- 
tremely difficult to seal the flasks so securely as to exclude air alto- 
gether, owing to the pressure of steam from the boiling liquid upon the 
neck of the glass softened by heat in the process of sealing. I found 
that often, when a flask seems securely sealed, air will enter through 
some minute aperture formed by the contraction of the glass during 
the process of cooling. By inverting the flask the entrance of the 
air may be perceived by the bubbles which rise through the liquid. 
The difficulty of sealing the flasks, and the impossibility of knowing 
whether a perfect sealing has been effected invalidates all experi- 
ments conducted with flasks filled and sealed by the usual method. 
In view of the difficulties attending these experiments, and the in- 
explicable results, I undertook, about a year ago, to work upon a new 
plan. In this series of experiments the utmost precautions were 
taken; the flasks, pipettes, etc., were all new and unused. Before 
using them they were thoroughly washed in acids, alcohol, and boil- 
ing water. ‘The objects to be attained in these experiments were 
PROCEEDINGS B. S. N. H. — VOL. XX. 7 MARCH, 1879, 
