66 
Pasteur and his Work, 
whose minuteness had hitherto either enabled them to escape 
observation, or to conceal their special function in the economy 
of nature ; and the origin of these wonderful living particles, 
whose operations are so vast and important in their results, 
could not but arrest attention. Indeed, the question of spon- 
taneous generation, upon which grave issues in pathology in 
particular depended, was one which Pasteur was in a manner 
compelled to take up. It was certainly one that had come down to 
our own day from lioary antiquity, but it was being debated with 
unusual warmth while he was successfully unravelling mysterious- 
processes, which he traced to the action of microscopical germs, 
whose source might be ascribed to a spontaneous or fortuitous- 
combination of elements. Aristotle was of opinion that all 
damp bodies which become dry, and dry ones which become 
damp, engender animal life ; Virgil thought bees were produced 
from the putrefied intestines of a young bull ; and, much nearer 
our own time. Van Helmont stated that the smells that rise 
from marshes produce frogs, leeches, slugs, &c., — nay, he had 
even the temerity to assert that mice could be produced by 
keeping a dirty shirt in the mouth of a vessel containing a 
little corn, which is transformed into these creatures after a 
number of days — he had witnessed it I and scorpions could be 
developed from crushed herbs placed in a hole in a brick I In 
the last centurv, Xeedham maintained the doctrine of spon- 
taneous generation, but Spallanzani opposed it ; Redi, an Italian 
naturalist, showed that maggots are not spontaneously developed 
in meat, but come from the eggs of flies. The introduction of 
the microscope was seized upon by the " Spontaneists " to 
support their notions, as in no way could the appearance of 
animalculae in previously barren fluids be accounted for. ^lis- 
takes might have been made with regard to the origin of mice 
and maggots, but it could not be so in the case of microscopic 
living things. How, except by spontaneous generation, could 
the presence and rapid multiplication of these in decomposing 
animal or vegetable substances be explained ? Buffon even lent 
himself to this doctrine, and devised a system in explanation of 
the hypothesis. In 1858, Pouchet, Director of the Museum of 
Natural History at Rouen, declared before the Academy of 
Sciences that he had succeeded in demonstrating, in an abso- 
lutely certain manner, the existence of certain microscopic 
living organisms which had been developed without pre-existing, 
germs. 
In a series of ingenious and ably-conducted experiments, 
Pasteur demolished, one after another, the arguments of Pouchet 
and the other heterogenists, by convincing demonstrations. 
" There is not one circumstance known at the present day," he 
