n the
experiments.

But Abbe Spallanzani thought that he detected such slips in Needham's
experiment. The possibility of such slips might come in several ways:
the contents of the jar might not have been boiled for a sufficient
length of time to kill all the germs, or the air might not have
been excluded completely by the sealing process. To cover both these
contingencies, Spallanzani first hermetically sealed the glass vessels
and then boiled them for three-quarters of an hour. Under these
circumstances no animalcules ever made their appearance--a conclusive
demonstration that rendered Needham's grounds for his theory at once
untenable.(2)

Allied to these studies of spontaneous generation were Spallanzani's
experiments and observations on the physiological processes of
generation among higher animals. He experimented with frogs, tortoises,
and dogs; and settled beyond question the function of the ovum and
spermatozoon. Unfortunately he misinterpreted the part played by the
spermatozoa in believing that their surrounding fluid was equally active
in the fertilizing process, and it was not until some forty years later
(1824) that Dumas corrected this error.

THE CHEMICAL THEORY OF DIGESTION

Among the most interesting researches of Spallanzani were his
experiments to prove that digestion, as carried on in the stomach, is a
chemical process. In this he demonstrated, as Rene Reaumur had attempted
to demonstrate, that digestion could be carried on outside the walls of
the stomach as an ordinary chemical reaction, using the gastric juice
as the reagent for performing the experiment. The question as to whether
the stomach acted as a grinding or triturating organ, rather than as a
receptacle for chemical action, had been settled by Reaumur and was
no longer a question of general dispute. Reaumur had demonstrated
conclusively that digestion would take place in the stomach in the same
manner and the same time if the substance to be digested was protected
from the peristalic movements of the stomach and subjected to the action
of the gastric juice only. He did this by introducing the substances to
be digested into the stomach in tubes, and thus protected so that while
the juices of the stomach could act upon them freely they would not be
affected by any movements of the organ.

Following up these experiments, he attempted to show that digestion
could take place outside the body as well as in it, as it certainly
should if