GEttERA^CH^RACTERS OF MICROORGANISMS. 
sicfemg bfip Jact thkt;he had only simple lenses to work with, 
were remarkably correct. Even his suggestions concerning their 
nature sound quite modern and were certainly superior to much of 
the speculation that followed. He intimated that they might be the 
cause of disease. But for 150 years after Leeuwenhoek, although 
the microscope became a familiar plaything, it was hardly thought 
that these minute organisms offered a subject for serious study. 
For a century they were simply objects of speculation, and many 
were the exclamations which they excited as to the wonders of nature, 
with here and there a suggestion as to their possible importance in 
producing certain natural phenomena. 
Relation to Disease. Not until toward the middle of the 
nineteenth century was it conceived that the microscopic organisms, 
at first grouped together under the general head of animalcules, 
could have more than scientific import. At that time there began 
to appear suggestions as to their possible relations to certain diseases, 
and almost simultaneously they were thought of as causing fermen- 
tations. Even before it was known what yeast was, it was recognized 
as in some way associated with alcoholic fermentation; but not till 
about 1838 was it clearly proved that yeast plants are the cause of 
the fermentation of sugar. The development of a knowledge of 
bacteria followed a little later. One of the first real contributions 
to a knowledge of their significance was the demonstration in 1840, 
of the fact that certain microscopic organisms cause blue milk. 
Thus, at the very beginning of the modern study of bacteria, they 
were associated with peculiar agricultural phenomena, an interesting 
fact when we notice that, in the next quarter of a century or more, 
the chief investigations, and all the interest in them, centered around 
the question of their agency in producing disease. Bacteria are 
still suffering in reputation from the fact that, for thirty years, they 
were studied by microscopists chiefly from the standpoint of their 
agency in the production of disease. It was quite early suggested, 
and soon demonstrated, that these little plants have the power 
of producing certain dreaded diseases, and the reputation which 
they thus obtained still clings to them. The very word bacteria, or 
germs, has become, in the minds of some, almost synonymous with 
