THE GENERAL' CHARACTERS OF MICROORGANISMS. 



considering the fac! fnat "lie* 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 animalculce, 

 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 



